For the
Leon Mk2 Aero/
K1 Kit your talking a lot of money. The price varies upto around £900 and spraying and fitting would be another £500+ at least.
Depending on the model of your Mk2 you may have to have a custom exhaust made up or could use a 2nd hand one from a TDI model or
K1 depending on if your car is Diesel or Petrol. So factor in at least £200 - £300 for the exhuast.
Total cost would be £1600 - £1700. This is all a
guide price.