So an update on the progress to date. I fitted new brake blocks, put some air in the tyres and went for a ride, which served to confirm that the frame is definitely too big. Plus the seat post was stuck.
So a few weeks of looking on eBay turned up this 52cm Peugeot in a fetching shade of blue.
No idea what model it is, despite looking in the catalogues on here and images on the net, but its lack of rainbow colours of other Peugeots is interesting. Sticker says Reynolds 501 though and looks legit enough.
So the Raleigh got put in the stand and the strip down started. Usual nonsense with the crank arm being seized on to the rusty bottom bracket, but other than that it was simple enough.
Turns out the BB is JIS (Shimano) and the cranks are ISO (Campag Mirage), but it needs a new BB anyway, so will be putting in an ISO one. I'm also tempted to treat the new frame to a nice pair of chrome bars rather than swap out the black Raleigh ones. I could then sell the Raleigh frame with the (stuck) seat post, stem and bars meaning it would just need a groupset and wheels. Assuming a frame like this has any interest of course.
So currently bike looks like this:
Very pleased with the results so far. Looking forward to getting out and riding.