There are different free buses that serve the various terminals:

http://www.heathrowairport.com/stati...d_Heathrow.pdf

I think that the more important question is this: Is the time you would spend making the sloooow Tube commute to and from Central London a good use of "prime" visitation time? To me, being able to stay in the heart of major world cities is one of the best reasons to earn points - in other words, to be able to afford a stay in a prime area that you'd otherwise struggle to afford. What's the better approach - starting your day with an arduous transit ride, or stepping out of the Churchill and being a block from Oxford Street?

One other thing - staying in tthe center city makes evening activities much more feasible - whether the theater, opera or dance, or just a nice meal at a non-airport-hotel restaurant, a central hotel gives you many more options.