On the note of the spa entry times, I was talking to Raffles about this as he too was restricted, but I was not when staying there. I contacted the hotel and they said:
Our complimentary bathing hours have always been 7am-9am and 8pm-10pm for all hotel residents. To access the facilities outside of the restricted times a spa treatment must be booked per person or a day pass purchased at £70.00 per person.
Some of our room types- Bath Spa Room, Bath Spa Suite and Feature Suites come with unrestricted access to the Spa Village.
So I still have no idea why I had no restrictions in place during my stay, but the spa was still mostly empty the entire time even when I assume almost everyone else had access too. Charging £70 per person to visit the spa area is awfully mean though when you're already a paying hotel guest; it would make me reconsider staying. I can only remember one other hotel doing this and it too left a bitter taste: MO Tokyo. At £150 for 60 minutes you are right at how expensive that is - that's £20 more than The Bulgari and £10 more than The Connaught, both of which are in the most expensive areas in the country with much higher wages.