For best results ide not bother with an actual tuning company. Ide get a map specific to your car, Pay a decent mapper to sit in the car whilst you blast about.
And the K04 kit aint as cheap as it sounds.
1) Turboback exhaust or decat £1000+ Unless you decat
2) The actual Turbo £1900
3) An uprated Intercooler £300+
4) Prolly need uprated injectors. £100
5) You will defo need a new set of brakes to be able to handle the power or your car will just be outright dangerous. Standard GTI breaks are rather pathetic. £1500 +
Prolly like a 4-5k bill right there