I have looked at many of my competitor airbnbs on land registry and all charges seem to be standard BTL so seems as though many or most do just use BTL mortgages even if not proper.
You are probably right there Doug but that doesn't make it right or mean you should copy them - on the same basis that you see many people do 90mph on a motorway but if you copy them, that doesn't mean you are not going to get a speeding ticket if you get caught.