Mid to late 80's Peugeot mid level models like the "PGN" with good Reynolds 501 CrMo tubing should be easy enough to start with as I think they have already trasitioned away from French sizes and threading and into British standards. which makes parts fot it easier to find.
Lots of these mid level Peugeots regularly go for auction at eBay so it shouldn't be such a hard bike to search for.
Other good candidates would be mid level Treks. mid to late 80's Trek 400, 550 and 660 series bikes were well built and a lot of bang for the buck. They seem to be more sought oafter than Peugeots, so the search for them might be a litle bit more challenging. You could go for the lower models too but you will need to make sure you like what you get with them as some models might not have full brazed-on fittings.

Good luck!

Chombi