Eventually finished this project of and am happy with both finished item and price!
Bellows - 30 quid, X2 Tele converter - 140 quid, 50mm lens - free, ringflash - 30quid, aperture actuator - free.
Aperture actuator, made from an old lens cap, a spring pick up thingy and some odd bits from work.
Aperture actuator fitted, showing how it passes through the cap and butts up to the actuating arm.
The finished article!