If this is on a Mkiv there is a good guide on ukmiv's, basically you can upgrade but not downgrade.
The short version is that you can put newer clocks in an older car but you can not put older clocks in a newer car. If you watch for where the immobiliser symbol is when you switch the ignition on it will tell you at a glance what immobiliser system you have, if the symbol is in the rev counter they are Immo 2 so you can fit another set of Immo 2 or upgrade to Immo 3 clocks, if the symbol is in the speedo they are Immo 3 and you need to replace them with Immo 3 clocks.
Or you can check the part number of the cluster with VAG Com.