the Syncro rear suspension set up is completely different to the 2WD Golf set-up. It's independent as opposed to the rather primitive beam on the 2WD.
As someone's already said - you need a Rallye kit from UK suppliers, although you might need slightly softer springs, as the Syncro isn't as lardy as the Rallye.
Why do you want coilovers anyway?
Let me know if you want to sell on the suspension you currently have.