Basically, apart from a couple of hotels that are connected to terminals (the Sofitel at T5, the Hilton and Yotel at T4), all hotels are within the perimeter of the airport. Generally they're not walkable (there's a handful of exceptions).
Several years ago, to ease congestion, the airport authority banned the hotel-specific shuttle buses in favour of the 'Hoppa' bus routes that took in multiple hotels on a schedule. This started off well, but then got contracted out to a private company who charge rather a hefty fare for passengers.
At the same time, Heathrow made it so that public buses passing through Heathrow were free within the airport area. So you can just hop on a bus at T5, take it to the Bath Road, and it costs you nothing. These buses go on towards other parts of London or surrounding towns, don't stop in the hotel forecourts, don't go directly from T2 or T3, and so aren't quite as easy to navigate. But they are free and generally more frequent. Here's a guide:
http://www.heathrow.com/file_source/...d_Heathrow.pdf
To use them, you just walk on, state your destination, and get nodded on.
Taxi is possible, although some may make it difficult for you due to the short fare. Taxis off the rank get a pass if they are back after a short fare, so may be OK. YMMV.
I'll have a look at your specific hotels. Which terminal(s) are you using?