Hi Chris,
Pro Pistons are a worth while investment at £3. You can then run the team setups
I suggest you try a combination of things.
A Carisma hard front spring, harder rear sway bar, run the rear camber link position on the inside hole at the hub and add some weight to the centre of the car.
Either add some lead weights in the middle or purchase a brass weight such as the one I sell at Thumbs Designs. Around 30-50g is a good weight to add. It really plants the rear end of the car in pretty much all conditions.