Thanks for the interest.
The frame is Reynolds 531 (according to the sticker at the top of the seat tube).
I'll remove the headset and have a closer look at the forks, hopefully that will yield further info. I contacted Mike Kelly (Cav''s early mentor) and he confirmed the name on the top tube is no relation, although he also confirmed there were two more MK's racing around the Isle of Man at the time and he knows both of them. Might try to find out some more info.
The frame is too small for me, but was originally intended as a l'Eroica ride for the wife. In an interesting development however, she has now designated Tuscany as a 'boy's trip' and now seems uninterested. Nevertheless, I'd like to restore the Quinn and am considering options. I've used Argos in the past, but may investigate C&G and see if they are still worth a shout. A fellow l'Eroicist recently had his Condor resprayed in grey and white and very nice it looked too. However, I fancy something brighter for this frame.
I found some Campag hubs at the local tip and have had these built up with Mavic OP and double-butted spokes - not particularly period correct but with an eye on the rigours of the Strade Bianchi.
I also have a Campag groupset and 3T finishing kit from a previous project, but again will have to have a longer think about that.
Will keep you posted.