I've stayed at most Heathrow hotels at different times and the Ibis once. It is good for an Ibis and they were pretty switched on there when I was there about 18 months ago.

I loathe the embarassment of a welcome to the UK that the "Hoppa" service is and remember that Ibis have a competitive rate with a local car service to the airport. If I remember correctly it was about 15-20 quid for a saloon car. Might be worth contacting them to see.