Vixpy1 (Charlie) runs Surrey Rolling Road. I've no idea if he does a lot of mechanical repair work on Subaru but he certainly knows his Legacy. Alternatively there's Greenwood Racing. Both in Surrey.
If you don't mind a bit of a drive Andy at Millers Autocare in Epsom (http://www.millersautocare.co.uk/) looked after my Skylines and did some major jobs such as intercooler fitting and manual gearbox conversions. He is a good bloke and will sort you out.
