There is no VAT on residental rent income. Hosts can use the rent-a-room tax allowance in the UK, up to 7K or so.
If you operate AirBnB as commercial let - Furnished Holiday Let (FHL) then VAT applies, but not below income of 85K per year.
If you lettings business has annual sales above £85,000 in the UK, you must register for VAT and add VAT to your prices.
You can then also recover VAT on purchases for your business (phone, computer, repairs, consumables etc).
If you wish to simplify the VAT process, choose the fixed rate scheme which avoids all the paperwork. Instead of paying 20% to the taxman, you pay a lower figure like 10.5%, which is generous. An IT business for example, would have to pay 19.5% (almost all the VAT). The % is different for each industry sector, and the govt recognises FHLs use a lot of stuff.
Quite separately, AirBNB as a business itself, must charge VAT on its service fee. This is unrelated to you, the host.
For most people, letting a room on AirBnB would be best as an individual (sole trader), as there is no tax and simple accounting. for multiple properties a Ltd Co. to let your Airbnb rooms would make more sense, as you can recover VAT on your purchases, use the dividend allowance and so forth.