How do Rich and welcome.
Engine mods wise, i'd advise a
Fidanza flywheel
JWT S3 cams
Full 2.5" exhaust system inc header and downpipe.
Sentra "test pipe" from the US as a de-cat.
Apexi Air Filter
Now these sort of modifications aren't cheap for the amount of gain but combine them with some weight reduction and you'll definitely feel the difference.
Just do some simple searches and all will be revealed on the above. Short of that you can turbo the car in two ways, adding a turbo to the stock engine or dropping a lump from a GTi-R in. Both time and wallet consuming.
Best mod you can do is a £16 membership. Will save you plenty if you;re in it for the long run.