1.4 TDI Starting problem!!!!!

have a 51 plate 1.4TDI (deisel) Arosa which until now has run like a dream. (The other night after visiting a friend) On turning the ignition key to engage the starter motor the vehicle starts!!! but immediately cuts out when you let the key go into the normal setting for running. The battery light also ignites up when it stalls.
This is my first post on this forum and Iam looking for a bit of product knowledge to save me going through a long and labourist process when one of you may have had this problem in the past.
Thanks in anticipation!

Hey,
iv got a 52reg and had the same problem. I stuck in 3 new heater plugs and a new barrel and it worked a treat. Hope this helps you.
Billya

sorry fixed it a while back tried my spare key thinking it was immobiliser problem it was!!!!!!! started first time with spare!

Turned out to be small immobilser block fell out of key when changing batteries for central locking!!!!!

Luckily found it on floor put back in key and hey presto all working again thanks!!!!