Thanks Willyam1,
Removed some hundreds of screws to reveal a couple of signal panels, audio one had no noticeable regs, other one had several. Gave up when eyes crossed. Perhaps next time when I have screen smash panels from the local tip to do a panel swap, and/or shematic, will give it a serious try.
Well, owner (Young Norfolk Farmer) didn't want to spend any real cash - they never do.
Thanks again Willyam1, and back to that Sliding (LG) jobby - Chris.