Okay, I finally had some time to look over everything again. All wires properly soldered. Just in case I resoldered some joints, removed some solder where it seemed excessive. No change whatsoever. I started to question my sanity.
UNTIL............
I looked at my meter and realised that it was in the wrong setting (AC)!
Well, problem solved. All V are easily within 10%. It must have been running perfectly from the beginning.
Not much lost, except some of my pride (well deserved I may add).
Thanks PB for the very quick responses and patience!