Hi Phil,
That'll be one of the expensive services then, with the cambelt change.....
NGK spark plugs are a good upgrade, platinum ones, not sure of the number tho, but I'm sure someone will be along to add to this anyway. As for oil, Silkolene is one of the best, but I think you'll find also one of the most expensive
A remap will up the boost, and front mounts are good for upping power as long as you don't mind cuttung up you bumper, although I do believe there are now smaller ones available so you don't have to do this - also you may want to think about upgrading the turbo as that will give you a bit more power too Don't forget tho, the more you upgrade, the more strain you put on your gearbox & clutch, look at Imprezyou's post, it's just cost him 2.5k for a new gearbox !!!!
Hope this is helpful, and as I said before, someone is bound to add bits or correct me
Pele