Guy's place was perfect. I went with my family, we were in 7 total (6 adults and 1 baby) and everyone was comfortable. Very well located (3 or 4 bus lines to touristic points or 12-15 min walk to underground stations), with a minimarket across the street, in a very residential neighborhood. Everything was working fine and Guy was always replying to every question/need we had.
If you're visiting London with a group, Guy's place its definitely a good choice.