I did see a share based at Cumbernauld which might work for hour building, but from the page on their site it sounds like you pay for every hour you have the plane rather than just flight time.
The page you linked says hourly charges are "block to block". That's a fairly common charging methodology which means flying time counts from the moment you first start to taxi to the time you shut down at the end of that particular flight. It doesn't mean you pay for the entire time the aircraft is away from home base, as your post suggests.
For example, if you were to fly from Cumbernauld to say Fife, have lunch there, then fly back, your block time for the flight there would be say 1 hour, and the same amount for the flight back. Total charge therefore 2 hours even though you "had" the aircraft for most of the day.