10mm spacers wont do ANYHTING for your handling, best not to use spacers wherever possible tbh!!
Also you may want to post in the suspension section lol
What are you lowerd on, just springs and torsion bar at the back?
Could look at geting some new shocks all round, stiffer springs, bigger anit roll bars, bigger torsion bars new bushes etc
Looking at WELL over £500 for a REALLY good setup, but for somnthing which handles well for road and the ocasional track use id say budget yourself around £300 and get new springs and shocks
EDIT god damned you Alex!!
Took me ages to write this lol
Oh and you could spend 100k on suspension if you REALLY wanted to lol