Hi,
@Thrupenney Bit, regarding the eye relief on the Optolyth 20x eyepiece, you can always unscrew the eye guard completely, which should ensure comfortable viewing with glasses (at least the Optolyth 30x eyepiece allows you to do this). A little drastic, but probably with good practical results.
@jring, thanks for the feedback! The Optolyth/Opticron combo performs very similarly to the Opticron MM4 77 ED with the same eyepiece. The tests I carried out also gave it some advantage when compared to an old Zeiss Diascope T*FL 65 with the 15-45x eyepiece (although this eyepiece is very nice because it's a wide one). And it eclipsed an Opticron HR 80 ED with the SDLv2 eyepiece, although I'm convinced that this was quite a lemon.
It's worth noting that I star tested the Optolyth TBS 80 HDF with very positive results.
In a subjective assessment, I believe that the combination with the SDLv3 (or v2) eyepiece is more appropriate with Optolyth HDF bodies.
Best regards,
Jorge