I have used Dan at
http://www.surreysubaruspecialists.com/ for the last few years.
Really nice guy, definitely knows his way around an Impreza. Provides a nice detailed write up at the end of the service and lets you know if there is anything that you might want to take a look at in the future based on inspection.
I don't use Facebook but I know he posts pictures up of what he is working on if you wanted to check him out.