'Compact'? 'Sheds'? Not true in all cases.
I've punted there since the '90s and in bedsits of various sizes, one bedroomed (with living room) and two bedroomed (with living room) apartments. Last time there was about three years ago (Elly, tall, slim, black girl) and there were two good-sized bedrooms, a large living room and good sized bathroom with shower and round jacuzzi bath. Many parts of the building have been upgraded, over the years, but they've kept some rooms for the low-rent trade.
I guess, like all flats in Central London, rentals for 'the game' have sky-rocketed, so more agencies are putting girls into the cheapest rooms. I'd add that WG flats, in Kensington would cost just as much. Cheaper out in W14, certainly, but too far out for the trade they want, as well as less chance of the relative anonymity, of CC or the mansion blocks of K&C. Buildings, like CC, were numerous, at one time but have almost disappeared in recent years.