I stayed at Roberto's place for nearly a month and it was excellent for my purposes.
It's a small studio at the top of the house but has the space and amenities needed for one person. There's a kitchenette with two burners, kettle, microwave and fridge for cooking meals, a TV with cable channels, and a closet and chest of drawers for storing clothes. There's a big window which brings in light and nice views.
You share the front door entrance with the family, but once you're upstairs and close the door to the flat you have complete privacy.
Roberto was very kind and helpful, picking me up at the Tube station when I arrived, and letting me use his washing machine for laundry.
It's about a 15-20 minute walk to Golders Green tube, but there are two buses that you can take from nearby Hendon Way to the station if you don't want to walk. If you don't want to take the tube, there's Bus 113 from Hendon Way which goes into central London, finishing at Marble Arch. If you head in the opposite direction from Roberto's place, there's Cricklewood Overground station.