as said further up. speak to vw tuners and tell them what you've got. you should be able to find one with a emulator. there is awesome gti in manchester but they are out of your area.

an emulator emulates (or pretends to be) a chip. the pc hooks up to the emulator and gives it the info to run the engine. the ecu then asks the emulator for the info. you make your adjustments to the info on the pc and the emulator passes the changed info to the ecu.