If for any reason you must arrive or depart with Terminal 5 at Heathrow Airport, one must strongly consider checking in at the Sofitel. A quick convenient walk from Terminal 5 makes location a key but more than that, the hotel itself delivers a great all-around tranquil experience. The hotel is definitely modern in decor but most importantly, the bed was exquisite - we stayed there after nearly 24 hours journey from South America and it was a truly relaxing experience.
The breakfast buffet was extensive and excellent. The fruit was fresh, the bread baked in the morning and the juices squeezed recently. The service perhaps could have been slightly more attentive but that is simply compared to other British hotels, where service has really been amazing.
One disappointment was that we were offered an upgrade to a suite from the regular room for £100 and we accepted the upgrade. But upon entering the room, it was not a suite - it was simply a larger standard room. I would not recommend upgrading to the suite, especially for the price. Also, if you are going to rent a car and park at the hotel, please ensure that you receive the hotel guest price, otherwise you will pay more than 3 times the price for parking.
If you are using Terminal 5, staying here is definitely recommend.