Anyhoo, a quick fettle before tomorrow's bun run with the cycling club. The saddle was as far forward as it could go. So I've moved it rearwards 10mm. Not sure if this means my knee is still over the pedal spindle (or even if KOPS is really a good thing to have or not). Will leave the 100mm stem as it is, and see how I get on with the saddle moved back 10mm. I did mark the original position with some leccy tape...
Of course, the ideal solution would be to go for a bike fit, although most of the places I've looked at seem to be more race orientated, rather than recreational bike fit... Anyway, I may well be changing the bike next year, so if I can make it do for just now, by playing with saddle fore/aft and perhaps changing a stem, then I can always get a bike fit when I buy a replacement bike next year...