Why is taking the train SO much hassle? Two changes, big deal. Beats the hell out of coach on the car park that is the M25. One caveat - if you do have a LOT of luggage then it might be easier.
I tried the RailAir coach link from Reading a couple of weeks ago... never again, it was late, dirty, and doesn't even go to T4
so you have to drag your suitcases up and down stairs, change trains... It's premium fares via Heathrow Express for me in future.