Hello @Colin103. I would have to google the regulations for the UK, but Airbnb does accept non-standard properties - there are even Hobbit dens for rent. It's all about diversity. The most important thing would be stating the height of the place in the description.
And here is what I learnt after googling:
"3. Minimum Ceiling Heights
Although the legal minimum ceiling height has now been removed from the Building Regulations, there is still a practical minimum height and this is especially worth thinking about in attic and cellar conversions. All rooms should normally have a floor to ceiling height of at least 2.1m throughout (standard ceiling height is 2.4m). In rooms with sloping ceilings, at least 50% of the floor area should normally have a floor to ceiling height of at least 2.1m."
// "The only person you can trust is yourself"