Where abouts are you matey?
I'm Northants based and there's a few that are quite good, not sure on price though.
RGS Motorsport - Wellingborough
3d Motorsport - Brackley
Veil Tuning - Northampton
Elite Motor Tune - Northampton
Depending on where you're prepared to travel to, yell.com yourself some quotes and use the forum for recommendations
TomB can probably advance on this.