Immobilizer/key troubles

[Roan]

Car is 2002 (B5.5/3BG) VW Passat W8.

I have a cut keyfob (came with car when purchased) which starts the car but leaves the immobilizer lamp flashing and will not open any doors remotely. I've googled but can't find out exactly what is going on... any ideas?

[Coupe_Daz]

Not coded, the blade section needs coding to the immobilizer and the remote locking fob needs coding to the central locking, dealers charge around £45