It's certainly a nicely built frame but it could be a lot wider potential build than Carlton or Rourke. There were many small builders in those days (and I'm starting to think late 60's/early 70's now possibly?) and in the Midlands/North Midlands area Paramount, Aelle, Sid Standard and others all built very good frames with a variety of seat stay top details. It all depended on what the customer ordered. In fact Brian Rourke would possibly not have been in business on his own yet when this was built. He started his own shop when the Clive Stuart shop that he was manager of in Stoke closed around '71?
I'm still thinking that it could be a Time Trial frame with it having only a single gear boss and a largish single chainring. The wheels are probably an 'everyday use' replacement for a decent pair of 'sprints and tubs'.
It's a nice little bike, well worth some TLC.
Today is the yesterday of tomorrow.