Hello again !
Tony at 'Axes 'R' Us' kindly e:mailed me the solution. On the old style Nashville 'Soapbar' bridges found on 70s S.G.s and Explorers, ( imagine a bridge that is a slab of steel about 1" front to back ) - you :
Screw the saddle forward from the back. When the saddle hits the front of the bridge, it 'bites' and then the rear screw head in which your screwdriver sits starts to unscrew itself, allowing easy removal of the saddle. I attach a picture of the bridge in question.
He reminds me that on a newer ABR type, there is indeed a clip that needs to be released before the saddle can be unscrewed.
I went for straight chrome plated ( brass / steel ? ) saddles on this occasion, as I did not know the merits of TUSQ e.t.c. Thanks for the info though Jazzrock. Had I know of tusq AND the repairability of the old saddle, I would probably have spent the new bridge money on repairing the old one with tusq saddles, especially as the S.G. it's going on is already a very smooth and slinky guitar .
I had already purchased a new Nashville bridge from WD spares, but this new ( Japanese) part has soft screw heads and threads. In contrast, the original bridge is made in West Germany and is hard as nails. Seeing as the old style 'soapbar' bridge seems to be in shorter supply these days, I wanted to bring the old German one back up to standard. As good as it was, it had seen over 31 years of string wear and over eager adjustments.
Thank you for your interest !
Regards,
F.F.