Interested to see how this turns out. I would suggest going berserk with framesaver on this and keep a close eye on it if you want to ride it in UK weather with tatty original paint...I worked in a shop which sold a lot of Vetta back in the day and even ~3 years ago still had about 10 early 90s Vetta frames in stock; a few of those were developing rust bubbles around the lugs and BB despite spending their lives unbuilt in a warm, dry shop. Their paint and prep back then was pretty inconsistent.
Very cool frame you have in your possession. Columbus MS is silly rare (almost as rare as AIR) and should make for a very nice ride (unlike Columbus AIR). I would build it up and ride the bike for a (part of the) season first. If you like it - and the geometry, sizing, etc. - then give it a respray.