There are dozens of airport hotels round Heathrow, from the Skyline Sheraton (me and my friends used to go and drink in the cocktail bar there) all the way down to an Ibis. It all depends what you want to spend cruiser. I would google airport hotels Heathrow and then look for reviews, maybe on Tripadvisor
I have used the Holiday Inn, Park Inn and Ibis down the years. The first two were Ok and with airport shuttles, the Ibis was a bit 'aircrew' with transfers going on all day and night. Not too bad if you are a sound sleeper.