Looking back on my late night post (last night), the reason why Carlton sprung to mind was the rear seat cluster. It's not wrap round as the seat stays are not joined and this reminded me of the Carlton Flyer. Carlton did build bespoke and frames to be built up into full bikes and not just mass produced stuff.
This was an unusual seat stay design as the 1960's went into the 1970's ....... full wraparound or brazed to the side were common as were shot in and the then starting to become fashionable fastback.
I Raced a 1970's Woodrup and it had fastback stays and a fully sloping fork crown, your crown is quite traditional...strangely the rear brake stay is not round.. By then the mudguard eyes were usually ground off.
Whatever it is, it never left a factory and was built properly and well worth the 60 quid and some more investigation