As an update, the PERFECT fork came available on mother Ebay: an original Cannondale Tange touring fork for a 27" frame 'Dale! This will be prefect as I can use it on the 25" frame, and elevate the bars to the same height as if it was a 27" frame. I will need a longer stem however, as the TT is 1" shorter on the 25" than the 27". I'm using a 90mm stem on the 27" now, so 110-120 should do it fine.
I may look to have cantilever mounts brazed on before painting. At least I'd have 'em up front where it counts!
And, if I'm not happy with the 25" frame, I'll at least have a spare fork for my 27" jobs.
Anyway, it is an original fork. Now, I wait to see if it is Cro-mo or mangalloy.......
Thanks to all who replied. RIDE ON !!!!!!!!!!!!