@Ruth890 A B&B & an Airbnb are two very different things...................
Any spare room can be let on Airbnb, but a 'proper' B&B brings with it certain expectations, eg of breakfast, probably served, & a full Scottish Breakfast to boot! - Whereas MOST private room Airbnbs don't include breakfast, & those that do are usually help yourself breakfasts....
My nasty neighbour reported me to the Council for 'running an illegal, unlicensed B&B..... A chap from the Council wandered round & said "It's only Airbnb, that's just like having lodgers really, isn't it?"
Some 'homeshare' Airbnbs are just that - homeshare, like having a very short term lodger. (I know of one across the other side of the county run by a young lad that is a real doss house! Whereas mine is a cleaner doss house!) Obviously some 'proper B&Bs use the Airbnb platform to market their services....
If you register as a B&B, you are presumably liable to all sorts of rules & regulations..... Whereas Airbnbs are unregulated.
Why would you want to register as a B&B? What's wrong with letting two rooms on Airbnb?