I just recently came back from a quick trip to London and stayed at the LHR Ren. Two reasons really, first it was the cheapest in the city by a LOT and second (perhaps equally important) because they always do things well there. Upon arrival on Sunday I decided a walk through downtown London was in order so I went to venture out to the tube. I couldn't recall the bus numbers to get to the station and found that the concierge desk now has these cool cards made to help folks. I typically take the bus to the Hatton Cross station but this time I did the Heathrow Central station. This worked just as well as Hatton Cross so thought I'd share with everyone
If you are going just make sure you check with them but these probably dont change too often. Best of all it is free to ride, so if you dont have a pile of luggage this is way cheaper than the 9p round trip for the hotel hoppa.