The "difficulties" of travelling with luggage on a public bus in London are, in my opinion, frequently overstated on this forum. You can always find somewhere to put your luggage, even if it means standing, somewhat uncomfortably, for the few minutes it takes to go from the Bath Road hotels to Heathrow Central.

Particularly if I have an early flight, staying close to the airport gives me peace of mind that a problem with the signalling on the Elizabeth Line and Heathrow Express (which are increasingly common) won't affect me. I've just paid £54 for the Premier Inn at T4, which has some of the most comfortable beds I've experienced at any hotel.