Probably the best hair salons that I have been in London with overall experiences.
The staff very friendly, cheerful and professional, hair stylists (I'm always with Caroline), is the only hair dresser got my hair style right so far, even I have been some very top salons in London (Urban Retreat in Harrods, Daniel Hersheson, Vidal Sassoon in Mayfair), they just don't know how to deal with Asian hair texture and snap of the head of mine (I must admit my hair is not easy to cut, but when I paid near £100 to get hair cut, I am expecting the hair dresser know how to work on different hair textures and shape of the head whatever their nationality is).
Another good point of Trevor Sorbie salon is they train their assistant properly on very basic hair wash routine, which many of these salons are miss such small point, the assistants just quick wash customer's hair with no intention about how customer actually feel.
I truly recommend their service!