If you're looking for a quiet, out of the way, clean neighborhood book this spot. Others have mentioned the stairs, they really aren't bad, at all. The space is clean, there's about everything you'd need, as I stayed 5 nights without issues.
There's a Tesco 400m from the front door, a 5 minute walk to Pimlico station and 12 minute walk to Victoria station.
Having a tub in an English bathroom is also a huge luxury, enjoy that if you have a chance.