I stayed at STK Homes' studios in Fitzrovia. They were expensive, but given the impeccable central London location and gorgeous building, I can't really say the price point is unreasonable. And while it was just a studio, I was quite happy with the size given the location.
Because STK Homes is a corporate host, I noticed when I communicated with them, the staff often gave inaccurate details about the actual flat. For instance, they said there was no laundry when there in fact was. They said there would be a frying pan when there wasn't one.
They also were not too responsive. I often had to copy and paste the same message to elicit a reply. I also waited a long time for a hair dryer, though it was included in the listing. I told them a couple of times there was a continuous dripping noise from the toilet, which never got fixed during my month-long stay.