Slinky - I know BA 'allow' it at T5 but they escort you to the border - they do it once an hour so time it wrong and you'll have a long wait.
Think they also scan your BP so they know you have left airside - also means you have to comply with BA conformance on the way back in when you clear security.
ALadyNcCal - an option might be to drop your luggage at the left luggage in each terminal rather than lug them to your hotel and back - especially if it one of the off-site ones.
This will cost you £10 per item.
http://www.heathrowairport.com/heath...s/left-baggage