Great place, in great location. The flat was very nice and very convenient to Oxford Street, Baker Street and Marlyebone. Not too loud either, especially given proximity to a bustling area with plenty to do.
There is plenty of space and the furniture is pretty nice, with a good kitchen and huge dining table. Bathrooms were nice, with good showers). We stayed with two teenage kids, who shared the second bedroom and never felt cramped - they set it up as two single beds. Note that the bed in the master actually feels like it was two single beds put together, so there was a bit of a gap/dip in the middle - this was one of the few things we had any issue with though.
Be prepared to take some stairs (have to walk up half a flight to elevator, and then another full flight after getting off elevator - flat is on 4th floor but elevator only goes up to 3rd floor)…but it wasn’t too bad.
Overall, I would stay there again.