Did a little more searching for Alan "Pongo" Braithwaite and his brother but there's not much info...they built Aende frames in Nottingham or perhaps it was "Pongo" solo by then. Seems he was known for a really short wheelbase and close clearances (specializing it TT frames), so this ACS Paramount would not be typical of his (later) work.
Looks like a nice frame, and I'm more certain that those are Oscar Egg lugs, now.