I used to old KO3 that was on my car and sent it to CR Turbo's. They charged me £600 inclusive of VAT and delivery, they pick it up and drop it off for you, getting it tomorrow

Better to keep your old KO3s and sell it on, you can make some money back that way. Fitting a ko4 is abit more of a pain, different downpipe etc etc and these make the same power.