I will definitely stay here again. The best thing about Cartwright Gardens was it's proximity to the tube, busses, and trains (St. Pancras/King's Cross Station is a 10 minute walk), as well as the British Museum, British Library, Trafalgar Square, etc.
The accommodations themselves are delightful. Small, of course, but containing everything needed for a comfortable and affordable stay. The kitchens have basic necessities-dishes, cutlery, pots, pans, dish soap and cloths. Lots of storage space for unpacking. A fan, safe and blowdrier in the wardrobe. Ironing and laundry facilities in the basement.
I stayed here in July and it could get hot without air-conditioning. The window opens onto the street, facing a small park with tennis courts. As there is a language school across the way, the park and courts could get noisy at night, with the young adult language students hanging out there and other youth having loud conversations. If sleeping with a small fan and closed window isn't your scene, I'd recommend an air conditioned unit.
That said, the street and area are gorgeous. Big trees, quiet mornings, beautiful heritage buildings. Even wildlife! Keep an eye out for the green parakeet that lives in one of the trees near the tennis court.
The staff are friendly and willing to help in any way they can. One lent me their French Press for the week, which was a godsend.
Again: highly recommended.