"Everyone who runs a Bed and Breakfast business from their home? (In the UK this sector is huge)."

"everyone" and "huge" - can you put some #s or %s behind this statement? is it 5% of the homeowner population?

Don't know overall, according to Wikipedia here in Edinburgh there are apparently "several hundred" - which seems quite a lot for a city of less than half a million people. Having said that, Edinburgh does get quite a few visitors (~1 million overseas visitors a year).