eBay and Craigslist finds

^ I think a lot of us were :-)

It's probably late 60s or early 70s. You can get a better idea from the frame number on the BB shell. Vintage Campag Nuovo or Super Record, by the way.
Or Royce and keep it British

Royce is great British engineering, but was a bit later as they started in 1980 so would not be contemporaneous to the frame. But that is assuming you want to keep it period correct. Otherwise go for it!

Nice buy by the way.