I stayed at Qazi's annex for 4 weeks and I really satisfied about the experience.
Qazi and his wife were always available and really nice to me, he even took my to Rayner's Lane to show me where the supermarkets were located etc, collected my personal corresponde and took me to the station when I moved out!

The annex itself is small (a converted garage) but the space is really well utilised, it basically has everything but a washing machine (this wasn't a problem because Qazi and his wife offered to wash my clothes in their private washing machine, which was really kind of them).
The annex is in quite good condition and well heated, with a radiator and a heater at your disposal.
The ministudio works well if you don't want to share a flat and want something more independent, while looking for permanent accomodation.

Regarding location, the house is in Pinner, northwest London, 10 minutes or less walking to Rayner's Lane station, which is a link for both Piccadilly and District lines. It takes roughly 30 minutes to Hammersmith Tube Station.

Pinner is a really quiet neighbourhood, not much happening there.
It can be inconvenient if you like going out in the centre of London since, apparently, night buses only go to Harrow Bus Station, which is 40 minutes walking to the annex.

All in all, I'm very happy about staying here when I first moved to the UK and easily recommend it.