Being totally honest, I think M's place is OK for a (very) short stay.
Seeing other reviews, I was worried about dodgy people at the entrance of the building, which fortunately I did not see, but several times I found the front door unlocked.
The room (or flat according to London standards) is quite basic: a comfortable bed, a table and a chair. I had a small kitchenette connected to my room, which was a nice surprise. The room can feel quite cold when the heating isn't on, and the electric heater provided is quite useless.
My only big issue was the cleanliness of the bathroom; I found stains everywhere, dust, and also long hair from a previous guest. It's not reasonable to charge a cleaning fee, and rent the place with a bathroom in this condition.