Do the free stuff first:
tyre pressures
check your tracking
If your dampers are not doing their job then change them, it will transform any car if they are not performing. If they are alright:
Spend a little money £80:
Go for a Whiteline rear ARB. Adjustable if you want to play, non-adjustable if you don't. Change the rear ARB bushes and drop links at the same time.
Change your front ARB bushes for new OEM but leave the ARB alone. £15
Spend more money £250
look around for some second hand adjustable dampers and springs.
Grind out your strut mounts at the bottom (Search for "Coarse camber mod" as it annoys Stumo
) and add some more camber on the front and a little on the rear.
Dor the tracking again
Spend more money or at the first opportunity if your tyres are poor £400
buy 4 new really good all weather tyres. GtiR tyres are quite small so aren't that pricey.
I don't know how much you can do yourself but it isn't very expensive to create a reasonable handling R. It's quite easy to spend a lot of money and completely mess it up. I've seen more messed up cars than decent ones (Too low/stiff)
After that, save your money until something breaks on the suspension and fix it. Changing all the other bushes to powerflex is a reasonable idea but is also an expensive one if you are getting someone else to do the work.
Search on my username and you should find enough waffle to explain most things.
Jim