@biggs682 - you're right. Note to self: don't guess. I've measured the frame and it comes out at 23". I'll have been quite nicely specced originally noting the above comment that the current Campag 5-speed set-up isn't original. Not as nice as the 10-speed set-up on the Carlton Franco-Suisse I picked up last month but well above the basic level. If you'd like the frameset let me know and I'm sure we can arrange a hand-over; I'll be travelling to my Dad's at Bottesford in the Vale of Belvoir a lot over the next few months so that might make the hand-over easier.
This evening I've gone through the bag of parts supplied by
@Ponterob for me and cleaned up the Campag Gran Sport rear mech, with the shifter currently un-stickying in my parts washer. It's a
much better design than the Benelux one on the Franco-Suisse so I
might borrow it, or use a Nuovo Gran Sport I now have spare.