There is a wide choice in room categories - pictures are from a Heritage room, the highest standard room category in the modern wings. Manor and Grand Manor rooms are located in the original manor house, higher up there is a range of suites for those wanting more space.
What I liked about the room: spacious, very clean, comfortable Four Seasons bed, nice marble bathroom with separate shower, soaker tub, and toilet. While it is clear throughout the hotel that you are in the English countryside, there isn't an overload in matching floral patterns, which is a huge relief compared to some other hotels.
In terms of which room to pick though, from what I can tell the difference between Heritage and Garden/Mews rooms is not that big; a little extra space and a view of the grounds rather than the courtyard. Unless that means a lot to you, I'd leave the step up and do an activity / have a treatment / get a few drinks for the money.
Points for improvement are no free WiFi (not really a shock there - when is this going to change?) and outdated CRT-TVs in the room.
Once Park Lane reopens in Mayfair, with Canary Wharf in the east, the addition of a property close to Liverpool Street, and a countryside retreat, Four Seasons will have plenty of London-area options for its guests. (Ed. Note: We smell a hotel package coming!)