I have learnt alot about the subject of Key Transponders in my quest to get my flip key coded to the car..
I first read both the VIN and Immobiliser numbers from my car using the VAGCOM 'Instruments' screen.
I then spoke to my friendly
dealer, who simply took the VIN and Immobiliser numbers over the phone and applied for a SKC for me on the SEAT computer system. The SKC came back from SEAT a few hours later.
I then just used VAG com and followed the Ross-Tech procedure to code an IMMO-3 car. Worked a treat (eventually!!).
On the subject of Timsons, they can't actually code the immobiliser chips, as when they put my original key in their machine, no codes could be read. The guy said this was because it was a crypto key. He demonstated what happens with a non-crypto keys by puting his own Peugot key in, and loads of numbers came up. The SEAT keys are deffo crypto Transponders, which can't be cloned.
Best of luck.