Now the headscratching begins....
I managed to strip the other 36 IDF and sucessfully removed the throttle shaft and butterfly discs un-damaged.
The butterfly diameter is, in fact, 36.8mm for the 36 IDF (presumably because the disc doesn't close to a full 90 degrees to the venturi). Also, the disc seems to be ground (80 degrees?) around the circumference in order to form a good seal when closed. Two flats are then milled/filed into the butterfly along the axis of the shaft to bring the diameter at this point back down to a smidgeon under 36mm.
So, a simple flat 1.5mm disc it most certainly is not. This has made me think twice about having a set of four fabricated by the bloke in the shed with the lathe who I have yet to find!!
I may get lucky and get hold of 2 discs (all I actually need) and fixing screws from eurocarb, we'll see.
I'm pretty sure that there are NO replacement shafts left...in the WORLD so the question is: Do I have some fabricated?
It's an 8mm shaft turned down at each end for 7mm bearings (of which I now have 2 sets of 2). The 1.6mm 'slot' for each butterfly
could actually be substituted for a 'notch' as I don't think there is that much torsional stress (with the new bearings).
The option is to go for some more carbs but I would rather, actually, repair/refurb the ones I have.