I had an early morning flight from T5 and decided to stay overnight at The Sofitel, Heathrow. Perfectly adequate and clearly very easy to get to T5. Both check-in and check-out was nice and easy. Rooms comfortable.
The only downside was how loud the air-conditioning was in the bedroom. It was so loud that it was impossible to sleep without turning it off. When tuned off the room became increasingly hotter and uncomfortable. Not a great nights sleep.
But I recommend the hotel for ease of getting into T5.More