Also recently had it fitted as well. Total cost £340.00.
A lot of money for what it is, but like others on here, I wanted it, so I did it.
As JPC said the problem is with the immobilsers and transfer of the mileage etc from one cluster to the other. You need the SKC (secret key code) to be able to do this. Darren has VAG Commander, which can read this code, but only upto (I believe 2006 model years). After that date, VAG changed the details on the clusters and after market software can't read the newer clusters, only the dealers (on in my case an independent) with the VAS tablet.
Cheers
Andrew