The missing socket arrived this morning. Full of will power I waited until after the days work was done before getting out the now rapidly declining box of bits. Socket in, C64 PSU tested, 9V tested good, so was ready to go. Small glitch until I realised that I had to change the core ID in MIOS Studio too, then all loaded smoothly. Fitted the 6852's one pair at a time, and ran through the sound banks, with a silly grin just getting wider on my face.
Still got a minor bit of front panel work to do, (3 spacers came unglued), and a little bit of fault tracing - the mix out doesn't seem to be working, but all is good, and the only last bits I need are 4 knobs for the feedback pots.
Now a lot of reading and learning to do. This thing is a small cased sound mainframe and I want to be able to drive it as it deserves.. Love the way my Korg Kontrol 49 keyboard loops up to a lot of the front panel controls too.
So very grateful to TK and Wilba for this.