If you are three or four people, you should be very comfortable with one another in pairs. The "double" beds are only 120 cm (47 in) wide. Also, the duvets provided are for the whole bed, so you should be comfortable sleeping under the same cover.
The oven did not work when we were there (never got adequately hot), so we had to give up cooking ourselves. The apartment was somewhat chilly, even though the radiators were turned all the way up (it was not very cold outside, maybe 8-10 °C), and changing the temperature on the thermostat did not help. Tricia from the "Skyline Team" (semi-automated management of the apartment, but apparently not the owner) answered our messages but did nothing about it.
On the positive side, the apartment is quiet, but only a short walk from a very vibrant party of Brixton, and Brixton Station which easily takes you to central London.