Hi everyone, sorry for the lack of responses on here... not had much time to be posting.
Not thought of doing anything yet, not sure what kind of gains I'd get from a TMC box (guessing about 200bhp) but that would probably be my first port of call. Closely followed by getting the wheels re-done in titanium...they look pretty for the first 8 seconds after they've been cleaned but I'm going through bilberry cleaner like there's no tomorrow!
What I would say to anyone thinking of getting a GPA SS though is just get one, they're great fun and easy on the wallet when it comes to tax, insurance and fuel economy. The ride isn't as harsh as many reviews suggest and it's just supreme fun.