Hi John I am going to throw my two penneth worth in, we have been plagued with VAG warning lights just of late and most have been traced back to the multi plug connections on the PCB of the dash board.

Just had my brother-in-law's Polo which spent a lot of time in Winchester getting nowhere running up large bills. The problem was intermittent coolant warning lamp which would randomly come on, also the key would not be recognised occasionally and would not start. The immobilizer light would also randomly light up when driving. No codes for the coolant light but the key would come up with aerial recognition & incorrect key codes. After studying the wiring diagrams we traced the relevant pin no's in dash & under a good magnifying glass you could just see slightly cracked solder joints, with a fine solder gun we sucked dry & re-soldered the joints and wala no more annoying beeps or lights flashing. We had a similar job not so long ago we solved another warning light but couldn’t solve the immobilizer but after installing a second-hand dash and this also cured the problem. Worth a look!
John Kennard.