For more than 11 months, Fiona Williams had carefully planned every last detail of her husband Mark’s 50th birthday.

They were to rent a large house for a week in one of their favourite places — Galway City in western Ireland — for them, their two children and eight pals.

Then, in the early hours of the day they were due to fly, Fiona was woken by a text. The 53-year-old accountant, from Ilminster, Somerset, said: ‘It had been sent at 1.30am and was from the host saying the booking was cancelled. Normally I’m fairly calm, but I was shaking. I woke Mark up. He was furious and started pacing around the room.

‘The host’s excuse was the neighbours had complained about the house being rented out. All the way to the airport I was messaging Airbnb to find an alternative. The only option they offered was six miles outside the city. It cost another £400 — and wasn’t available for several days after we arrived.’

It is ten years since Airbnb, the online marketplace which arranges short stays for travellers in other people’s homes, revolutionised travel. For cash-strapped holidaymakers, it’s been a godsend, giving cheaper alternatives to hotels in 191 countries.

But when things go wrong, some say they have found themselves left with little support or understanding of their predicament. Fiona felt stranded as she desperately called the firm asking for alternatives on a busy Irish bank holiday weekend last month.

After a stressful flight not knowing whether she had anywhere for her guests to stay, it was only when she arrived at Shannon airport that she managed to find a hotel several miles outside town.

She says: ‘Airbnb did give me a refund when the house was cancelled. But over that week, I paid £1,455 more on hotel accommodation, food and taxis in and out of the city. We’d planned it all so we’d be in the middle of town to enjoy the night life. Yet Airbnb insisted £200 was all they would give me towards those costs.’

A paltry sum considering the company has been valued at £24 billion and is said to be preparing to go public and start selling shares on the stock exchange. But as it becomes a global force, questions are being raised over its customer care.

One critic is travel researcher Asher Fergusson. He and his wife rented an Airbnb flat in Paris in September 2017, paying £780 for a week. But when they walked in, the sight and smell of mould was so overwhelming they left without unpacking because they were so worried for the health of their ten-month-old son Kingsley.

Guests pay for Airnnb properties up front, so Asher and his family had nowhere to stay and no money for a hotel, despite sending photos of the mould to Airbnb and asking for help.

When Asher, 32, tried to rent another property, the Airbnb host offered an alternative that looked nothing like the chic apartment in the pictures — and asked for cash, in violation of the company’s terms and conditions. It was four months before Asher got a full refund.

He then analysed 1,012 complaints about Airbnb. Of these, he found over a fifth were triggered when hosts cancelled a booking 24 hours before it started or didn’t turn up to let guests in. One in seven involved ‘unsafe’ conditions such as infestations, mould or intimidating hosts.

A report for the European Commission last year analysed the main problems for consumers. It stated: ‘Over 40 per cent of users of Airbnb experienced one or more problems at least once over a 12-month period. The most frequent related to accommodation not being as described — 19.1 per cent; — poor quality rentals — 17.8 per cent; cancelled reservations — 11.2 per cent.’

These statistics, too, are dismissed by Airbnb as ‘completely false and dangerously misleading’ as the sample of 736 users comprised ‘just 0.0001 per cent of our over 400 million guest arrivals’.

The company said: ‘We strive to provide exceptional customer service. With over two million guest arrivals staying in an Airbnb every night, incidents and issues are incredibly rare.’

While the frequency of such failures remains a matter of debate, those affected can see once-in-a-lifetime celebrations wrecked.

For Shaunna Lee, her sister-in-law Sam’s surprise 30th birthday was ruined when the host cancelled their stay 15 minutes before they were due to arrive.

The plan was for insurance exam coach Shaunna, Sam and their husbands to spend October 27 in London, enjoying dinner and a West End show before walking to a swish rented apartment in Soho, costing £215.

Shaunna, 26, from Saffron Walden, Essex, said: ‘We were due to check in at 3pm. At 2.45pm, I saw an Airbnb message from the host. She said the booking was off due to a problem with the bathroom.

‘I froze. When I said it was cancelled, everyone thought it was a joke. Then my husband said: “She’s serious. She’s gone white.” I rang the host, who insisted we couldn’t stay. I heard a foreign ring tone, which was odd, as she was due to let us in.

‘She said my issues were with Airbnb because she’d already refunded the rental fee to them.’

Over the next three hours, the group racked up a £40 bill ringing Airbnb’s customer service line.

Shaunna says: ‘They were so unhelpful. They wouldn’t say when they’d call us back and when they did, we got cut off. About two hours later, they sent two alternative Airbnbs. The first was on the outskirts of London, and wasn’t even available. There was no link on the second.

‘We started calling hotels but they were either full or would have cost over £1,000. Airbnb offered £30.18 to find somewhere else, which is laughable. Then my sister-in-law remembered a cheap hostel. By the time we got there, we’d missed her birthday dinner, complete with prosecco, waiting for her.

‘After I got home, I told Airbnb I needed to be reimbursed for the extra cost of taxis, our accommodation and phone bills. Finally they agreed £150. But the experience tainted our memory of Sam’s big birthday.’

A holiday to New York last month was also meant to be the trip of a lifetime for Josephine Forster, who was attending a close friend’s wedding with her husband and two other friends.

To save money, the 29-year-old writer booked an apartment in the East Village via Airbnb, instead of a hotel. But a few days into the week-long trip, all four started to notice an unusual number of insect bites. ‘We put it down to mosquitos,’ says Josephine, from South London. ‘But the day after the wedding, we noticed blood on the sheets. I looked closer and saw I had eight bites. We realised we all had the same marks. There had been a bedbug infestation while I was at university, and it dawned on me this was the same thing.’

But the misery of being covered in bites was nothing compared with the stress of finding somewhere else to stay at short notice — and, above all, dealing with Airbnb, who already had the full £1,151 fee for the apartment.

‘We sent Airbnb photos of our bites. They agreed it was bedbugs. Over the next 24 hours, we must have rung them 20 times. We were passed around different people, put on hold for up to half an hour or cut off. The story kept changing, too. At first they’d said they’d help us find another Airbnb. Then they said they couldn’t, in case we were carrying bedbugs.’

By now it was evening and the group urgently needed accommodation. ‘Then Airbnb suddenly checked us out of the apartment — but without offering somewhere else to stay.

‘By midnight, I was crying, stunned by the treatment we were experiencing. Realising we were getting nowhere, we rang round frantically to find the cheapest hotel we could.’ They finally checked into a budget hotel at nearly 1am.

Other complications arise when the property looks different to its Airbnb profile. In March last year, company director Tony Totczyk and girlfriend Kirsty Hall paid £480 for a week in a flat in Tenerife. They were particularly drawn to the swimming pool.

Tony, 52, from Lymington, Hampshire, says: ‘It’s a reasonable expectation that when you book an apartment with a picture of a pool as a selling point, you’ll be able to swim in it. On Airbnb, the pictures looked excellent.

‘Once we arrived we were shown around very quickly. It was only later we realised there was no TV as described, and the wifi didn’t work. Then we saw the pool — it had no water in it.’

The couple rang the host, who did not return their calls until the day before they left. Tony says she spoke little English and gave no explanation. Once back in the UK with proper internet access, the couple contacted Airbnb.

Tony says: ‘They told us we hadn’t tried hard enough to complain to the host and hadn’t contacted them in time. When Kirsty sent a screenshot of one of her messages to the host, they said they couldn’t see the number on it.

Airbnb also told us we had no proof there was no TV or wifi, even though we sent dated pictures. They simply told us they were going to take her word for it.’

He adds: ‘They took weeks to reply to messages, and it took two months to offer us £120 credit towards another Airbnb, while the host offered us £84 for not being able to use the pool. We found phoning Airbnb near impossible. The idea is apparently to make it hard and hope you will go away.’

Despite all its glossy pictures of lovely places to stay, experts point out that Airbnb works mainly as a payment platform.

The company charges hosts 3 per cent per booking. According to their website, the service fee for guests ‘ranges between 0 per cent and 20 per cent.’ Lawyer Rob Dempsey, of Roythornes Solicitors, says: ‘Within the Terms of Service, which customers rarely read, Airbnb states that the contractual relationship exists solely between the holidaymaker and the owner.’

Consumer rights expert Frank Brehany says: ‘The internet is awash with experiences of what can happen when things go wrong. On reading those experiences, it is clear some consumers did not read the terms and conditions of what they should have done when they discovered a problem.’

That’s not easy — the EC report questioned the transparency of Airbnb’s terms and conditions, which are ‘37 pages long’. Get through them all, and you will learn that if your booking is cancelled, it’s at the company’s ‘discretion’ to reimburse the money and use ‘reasonable efforts’ to find you accommodation.

Josephine and Fiona have been fortunate. Until the Mail contacted Airbnb earlier this month, the company had offered them £200 and £100 each respectively to cover the cost of finding somewhere else to stay.

When we asked them to comment on Fiona and Josephine’s cases, the company approached the women directly to offer £1,255 and £689 respectively. In Josephine’s case, Airbnb said: ‘The level of customer service provided here fell below the high standards we set ourselves.’

In Fiona’s, they said there had been no complaints from neighbours about the property after all, but ‘the host accidentally double-booked their listing’. They added that they had now apologised.

In Tony’s case, Airbnb said he and his girlfriend did not contact them quickly enough, despite being abroad and pointing out that they had no wifi. The property is no longer listed on Airbnb.

They said Fiona was given a refund for the lost stay. Yet she says nothing can make up for her husband’s ruined birthday. ‘I will never forget how sick I felt, not knowing if I could find beds for 12 people. I never want the stress of using Airbnb again.

‘They say such cancellations are rare, but my husband only had one 50th birthday.’