Update:
The frame I tried to karma on here, which in the end has gone to the Bristol Prison Bike project had a seatpost that I figured was worth trying, and - whaddyaknow? It fitted...
Have managed to liberate a knackered old saddle that I was certain I'd thrown out.
Konaman - thank you so much for your time and trouble - do you mind if I just take the shifters/brake units? Could you PM me about payment for postage?
Sic_nick: no probs, fella - it sounds like a more than fair price, but at the moment I'm just not in a position to take advantage of them - shame cos they sound great. Thank you anyway.