I spent 5 days here in November 2012. I have stayed in 5 star hotels in London that didn't measure up to St Ermins standards. High quality fit out but retaining the charm and character of a traditional English hotel.
I can't speak highly enough of the staff. All extremely well trained and genuine hospitality professionals who really do take an interest.
A good gym facility that could be made excellent by simply adding a couple of swiss balls which would enable a full body work out with their free weights. An excellent selection of cardio machines, all with private screens, iPod/iPhone integration, charging and Nike+ integration.
The Caxton Bar & Grill offered a great selection of food that was well presented and cooked to perfection. I also had the opportunity of dining at No.11 Cadogan Gardens (A five star property near by in Sloane Square) which was very average in comparison.
The room (240) offered some great features including an interactive TV, good sized bathroom (for London) very comfortable bed and again great fit out. The only draw backs were that it was located next to the staff elevator/service area and I would be woken each morning by banging and crashing of trollies and doors opening and closing and there was a view over the hotel machinery plant and refuse area. My colleague who was only staying two nights had a beautiful view over the lovely gardens and entrance to the hotel on the 5th floor. Something to bear in mind for next time. One other small thing was that I had two housekeepers on two separate occasions enter the room without knocking. Admitably, the first occasion, I had the "please make up my room" sign out and the other occasion was 3 minutes after my scheduled checkout time. In any instance as a hotelier, I wouldn't accept any of my staff entering any guest room without knocking.
In a nutshell a great property which I will definitely stay at again and my very good rating could have easily been an excellent rating but for some very small operational failings.