So a few hours later and the Delta 300V 100mA PSU is working
Needed a couple of resistors, diodes and transistors from stock in addition to the bought in parts. It would be a bit of a pig to troubleshoot as the main PCD is behind the panel, hard to access and hard wired to front and rear panels.
Load test for full voltage was fine but on high current I thought I was only getting 20mA maximum until I checked the actual current and found the ammeter adjustment was well out. Full current at 40V out and the heatsink does not even get warm.
Nice little power supply.