Catman you should have tried the Sheraton Skyline which is the other Sheraton at LHR. It has much more comfortable rooms. As for the bus, it's run by the Airport transport agency so Starwood can't help you other than perhaps give you a free ticket for the return. However I've found that you can sleep in an extra half-hour by asking the concierge to have a car ready for you. For 8 pounds you can have a private car take you directly to your terminal. It's much faster especially if you have to go to T4 which the Hopper bus doesn't serve anymore.
I'm glad Sheraton is still serviing good amenities. They are great in Europe.