Hot start problem is in most cases caused by a worm starter motor. I had exactly the same issue with a 2005 Golf 2.0 Tdi (BKD) which was resolved by replacing the starter motor using a recon unit from ECP. Replacing the starter motor is a 30 minute job abd can be done on your driveway just remember to discount your battery first.
Thanks for that - will get looking for a new starter!