Hello Welcome to the forums. Where are you and the bike? Knowing if the bike is in the US or Europe would be helpful.

""At time of purchase, the bike was equipped with Campag record Hubs; Rear being a Route Super Champion Competition, high flange (with 1969 UK National Track Championship scrutineers sticker, not original to the frame which is some 20 years younger I think), the front a Fiamme Red Label, low flange.""

Do you mean the hubs were Campagnolo, the rear one being high flange with a Super Champion Competition rim? If all that super champion stuff was written on the hub shell it likley wasn't CampI.

You mid '90s BB looks like english threading to me, doesit 1.37x24 stamped on it? Italian would be 36x24.

If this is in the US my guess was this poor thing used to be a Fuji simply because they likely had more track frames here in the late '80s than anyone else escept maybe Bianchi. The English BB and 26. whatever leads me to think this is Japanese origin.