We had a very merry Christmas at Ben's place. There were five of us (all adults) and we found plenty of room for everyone. The beds were comfortable, the bathrooms were clean, the decor is cheerful, and overall, it is a very nice apartment.
The subway is about 400 meters from the building. It is a bit of a walk but the Jubelee line is very good and connects to all the tourist sites in the city without any problems.
The only problem we had was the lack of a table in the kitchen, which makes it a bit difficult to eat something there. Otherwise, I highly recommend it, especially for a family or group of five without small children.