The space is large & comfortable, especially for a London flat. The rooms are a decent size. The dining room is big enough to have your whole group be comfortable at table. The location on the top floor means there's a great breeze which keeps the flat cool, even without air conditioning! There's also a small lift, which is VERY useful for bringing luggage up.
London transit is very comprehensive , including the area the flat is located in. Even so, bring your walking shoes to explore the city, Hyde Park, and the wonderful museums which are all a short trip away.