Last night was the only chance I had to get to grips with stripping the BSF S60 since my original post and offers of advice.

1. Cylinder mounted in spring compressor, with my adaptor to fit snugly in the hole at the back of trigger block.
2. Take up tension of spring sufficient that guide block screw comes away easy (12mm open ended spanner to loosen off) - the block holds the spring under tension.
3. Easy off tension slowly so that the scope rail, trigger mechanism and guide block slides back at the same time and, dare I say it, until the sweet spot is reached where the scope rail becomes sufficiently loose to be lifted out of keyway by hand - no tapping necessary. If the spring compressor tension is released too much, the scope rail becomes tight again, because, releasing spring tension further, pushes the scope rail key against the end of the keyway. Just apply a little tension with spring compressor and hit the sweet spot again and out she comes!
4. Once scope rail removed, release tension further; out comes the trigger mechanism, guide block, spring and piston.

Stripping job done!

Mine didn't quite work as easy as that! At first, after removing the block screw, and releasing tension - solid as a rock, no movement - what the.....?

Application of Plus Gas on scope rail, trigger block and everything else, spring compressor tensioning, releasing tension, nothing moving!!!

Unscrewed the tiny scope stop screw in desperation...., backing off spring compressor about 3mm and, with a piece of wood, tapping edge of trigger block close to cylinder backwards, tensioning and releasing spring compressor many times, it eventually released, bit by bit. Once apart, I could understand why...the grease, or whatever it is, covered everything from under the scope rail, cylinder, block, main spring...everywhere possible. It had the consistency of a varnish or shellac that was nearly dry???

The grease(?) does not dissolve readily, but, I'll get there! Looks like it has not been stripped for many years. Otherwise, in very good condition throughout; screw heads, etc....leather piston seal is excellent, as is the piston and cylinder.

For interest, the spring dimensions as found:
Length: 234mm (9 and 3/16)
Internal Dia: 14.3mm (0.563")
External Dia: 21.2mm (0.834")
Spring wire Dia: 3.4mm (0.134")

Many thanks again for the help.

Best regards to all....