first of all 8 hours in heathrow is a long time, and dont even think of getting a day room at local hotel. Get your bags checked all the way through, then if you can get out of the airport, go into Windsor or even London for a couple of hours.
I have never had problems with BA except they lost my luggage once (on way home). Flights do tend to be full. Try and join their frequent flier club, as it adds a few benefits, such as faster check in, online seat selection, etc.
Just flew back with them last night and everything was fine landed at 5.15 and was out of airport by 5.45, and that was even having a chat with customs about all my cigarettes
