Right if you could get the parts Rocco diesel 1K8 920 972AX or Rocco petrol 1K8 920 972X or Rocco R 1K8 920 972DX plus the newer golf mk5 Cecm 3C8 937 049AB plus the latest gateway, plus get it all coded you would have it working and no problems.
Most dealers will politely tell you to get knoted but if you speak to Hazzy Dayz they have the right Vas equipment and access to vw direct tech to do the job, the clusters are £280 new and the cecm is about £250 but I'm sure you will find the last part on ebay cheaper, you will need a new cluster for hazzy dayz to do the job.
Darren