I've been playing 'Left Bank Two' for some time now, sometimes recognised as the t.v. theme for 'Vision On' in the '70s. I've transcribed it, and there is an arrangement out there, but, since it was recorded in the final bit of time left after a recording session, by Wayne Hill, I suspect there was never an original copy of the music. Listening carefully, it's clear that it was a sort of jam that worked really well. Does the original copy exist?
I doubt (but wouldn't know for sure) it has ever been published as a score, even if there was an original written score from the composer. It was recorded for the library music production company Music De Wolfe, probably on a work for hire contract, so the rights would belong the De Wolfe. They produced a vinyl cut of the recording:
These recordings from library producers were typically not for commercial sale but for demonstration purposes only, but the existence of the cut (and luckily, the availability of the label image online) shows that the company owned at least the audio publishing rights. It's almost certain that they would own full copyright. They still do own it by the way, the track can be licensed directly from their site.
Now, scores are not normally part of offer of production music companies, as that would cannibalize their mainstream business (selling the actual music), so it's doubtful (to say the least) that there would have been an officially published score for this particular piece.
Anyway, as I said I don't have definite proof that there never was a published score, but I think there's compelling circumstantial evidence in that direction.