The wraparound stay reminds me of Falcon, Carlton, raleigh and Urago.
But, it does not look quite right for any of them.
yes, it's very nicely done on this bike. That rules out Falcon from the era that I worked on them, mid-'70s to early '80s.
This bike is very nice, the only discordant thing I noticed was that they seemed have under-filled the bb cable sling a bit.
I don't think extensive braze ons really caught on until the late '70s, and it wouldn't surprise me to see a bike from the early '80s that only had bb slings and a cable stop on the rear dropout. Top tube housing guides, dt shifter bosses, and bosses for a DT bottle cage were pretty common by 1980, but maybe not from U.K. builders or old-timers elsewhere