FIXED 
I bet your thihngking great, he’s fixed it and not going to spill the beans like so many techincal threads on forums.
So.
I had a better look at the schematic, determined the opamp must just be acting as a biased buffer.
Not a lot to go wrong there really.
I was going to check the output voltage of the opamp, but thought I should check the power rails first. +12 was fine, - 12 was awol. It was awol on all the 74’s
I quickly checked my new PSU and that was fine
I then started looking at the board.
AHHHEMMMMM