St Athans was clean and comfortable, in a pretty central local in London. Communication was easy and they have free locked baggage storage onsite (although this is accessible to other customers). The shared bathrooms were very clean and always available.
Our only gripe was that our third floor room was much hotter than outside and had no air conditioning. The floors below us seemed fine.
There are also three flights of stairs (no lift) and the landing you must cross to the bathroom requires you to jump across a stairwell. This was fine for us but wouldn’t be appropriate for people with less mobility.