Hi PP, welcome to the club. Good to have someone close by, I live in folkestone.
I had 2pots on my 94wrx and agree with the rest, the performance is Best to save up for some 4pots or similar.
Most people seem to go for the Toyo T1R. I have these on mine and they are a great tyre
I had a full geometry set up done by Barrets Motorsport in canterbury 01227864537. Totally transformed the car
As for having 300bhp, i very much doubt it Your car comes with approx 240bhp when used in japan with their higher octane pump fuel. To reduce the chance of engine failure, dont run less than super unleaded and try and use an octane booster of some sorts. There is a rolling road on the old road through Capel-le-ferne on the way to Dover (SVA Imports, next to the plough pub) but have not tried this myself.
There are not many chip replacements avaliable for the early cars so you will probably need to get a fully mappable ecu fitted. The Apexi Power FC is a very good choice and Simon (Jolly Green Monster) can supply, fit and map this for you. Just send him a pm. (if not here try 22b.com)
Hope this is of some help. Thats what were all here for after all.
Nathan