I have only stayed at the Starwood London airport hotels a few times (both Sheratons), but having done that, I avoid them like the plague. You are stuck there with an expensive bus to the airport to connect to the tube; if you have any way of staying in central London at a reasonable price, I would do that rather than staying at the airport. The only airport hotel that I would consider as an alternative to central London is the Sofitel in T5 (which is obviously not a Starwood property).