guy had it in an estate with the intention of putting it in a mk1 golf, as far as i know i bought everything to do the swap :S
so i may need a new ecu aswell?
No you won't...
You can adapt the Mk3 ECU & Immobiliser using VCDS (VAG Com)...you go into the ECU/Immobiliser modules and into Adaptation.
Go to the 'Engine' module.
Select 'Adaptation'
Press 'Read'
Wait...
Press 'Save'
Go to the 'Immobiliser' module.
Select 'Adaptation'
Press 'Read'
Wait...
Press 'Save'
That's it...
You will need an immobiliser module, ignition switch ring and matching key if you are using the immobiliser type ECU....and of course, you will need the diagnostics hooked up and working.
I've had 3 different ECUs in my car, and re-coded the ECU/immobiliser every time...takes 30 seconds.