I went to look at some of them. I am basing this on Central's current premises in Clerkenwell as I don't think they will move yet... although I really wish they will.
Walmsley is smaller and therefore felt they would be looked after more. It is 5 minutes away from studios. Looked at 1 person, basic and mid rooms. There is a very small difference but not noticeable on sizes between basic and mid. The lady said if they are in first year then these sizes are fine as delux/gold are too much as they dont stay in much. My DD didn't like the bathroom as extremely small, like a caravan, all plastic where things would get wet. Very friendly and clean.
Drapery Place formerly Plaza.... again by Unite. A lot bigger place overall. Saw single rooms and they are a bit bigger with table for food and table for working. Bathroom much better also. However its 45 minute walk and they do have long days at Central. Tube we didn't do as walked, but tube would be Farringdon to Aldgate East, 3 stops, 8/9 minutes plus a little walking time. Again friendly and clean.
Paris Gardens. Saw this but didn't go in as they emailed to say they are not taking bookings for 2021/22 due to refurbishment. Looks nice, a quiet area and only 25 minute walk.
My DD prefers Drapery but I would like to see if there's anything closer. Hope this helps specially if you live outside UK.... would be interested in other people's thoughts and places.