I used points to pay for about 70% of the cost of a room that had club lounge access and used the tripadvisor voucher on this website for an upgrade.
Check in went smoothly and I was given an upgrade to a junior suite. The room was comfortable, especially the bed. There was even a TV in the bathroom.
We had room service and used the club lounge. Alcohol and food are served only at limited times though (in the lounge).
We managed a trip to Windsor via the Terminal 5 bus station before we flew the next day. The location is the best for terminal 5. Although other hotels have terminal 5 in their name they are not at the terminal. the Sofitel is.