I remember Maplin moving away from the Softy-2 and selling the cheaper ART unit instead. I haven't noticed much info on these, on the 'net - but not yey on the
http://matthieu.benoit.free.fr/ collection
However, attached are Maplin's 1991 catalogue pages with their details, for info. (Cropped + complete-pages also with Gang-of-8+ unit).
Maybe a scan of the manual / copy of the software posted somewhere may be useful for future reference, if not done already.
Regarding reading the Softy-2's firmware EPROM, in worst-case you could just use the unit to copy it's memory to user RAM, which can then be shown on the screen and some screen-shots taken, scrolling from start to finish as required.
If a couple of people retyped this in, then should be able to identify any re-typing errors.
I don't think it would really be worth going to the effort / risk of removing the soldered-in Character Bipolar-PROM, as I can't really see why it would have been any different from the one used in exactly the same way on the Softy-1 that S2 was really a slightly-updated version of.
So I'd be inclined just to verify it's contents in actual use - either by: Capturing the outputs relative to input pattern, with uC (may not have to be too high speed, if it just ran in a loop for a while and built-up the image over many samples)
Or maybe by just capturing a zoomed-in good quality screen shot of the font, and comparing it with that shown here:
http://www.theoddys.com/acorn/PROMs%...racter_rom.txt