From my reading Nell Gwynn have a handful of apartments in this building which they manage for private owners - for this visit we, as a couple, rented a 1 bedroom apartment. I know this area very well and the location is excellent for anything or anywhere you are looking to get to including central area for shopping or just south of the river. If you need to head east then the apartment is 7min walk to Sloane sq Subway (circle and district). If you are driving the building does have underground older style parking.
The building is an art deco type block with clean and modernised lobby area - there is a concierge there who takes care of the building as this is NOT a hotel but a building also run as serviced apartments ...... i think why if reading google maps there is some odd reviews (they are different owners and companies)
For the apartment we stayed it was on the 6th floor and was clean and had enough space for us as a couple. We note London apartments can generally run on the smaller size. Full function kitchen and all items needed. Living area and netflix capable. All items were in good repair and condition. Only item we didn't like was the Shower - it is the old fixed wall type - meaning if you want a shower but don't want to wash your hair you are stuck as it cannot be adjusted .... that is a specific to us and may not bother others but for a longer stay it may be annoying
Check and out was efficient and we could leave luggage with the reception of the building
Communications with the Nell Gwynn staff was timely, friendly and efficient
WE would stay at one of their managed places again