The British Library's Theatre Archive Project is "a major project to reinvestigate British theatre history 1945-1968, from the perspectives of both the theatregoer and the practitioner". Part of this is an oral history project, which can be searched online here.
I keyed Jackie's name into the search box, and up came this interview with actress Penny Francis. Here she's discussing her husband Derek Francis and his television work in the Sixties. (Doctor Who fans will know him as Nero from The Romans; he and Penny were apparently friends with Jackie and her husband Alvin Rakoff.)
"He died in '84 and in the meantime, in about 19… yes in 1961, or it might have been 1960 he was doing a series on television called The Six Proud Walkers, which was a very unusual 13-part serial, not series, serial. And it had the most wonderful actors in it like Tony Britton and Jackie Hill and oh… I can't remember – Andrew Sachs – who's been in the news recently. And it was a wonderful, wonderful cast."
I've seen The Six Proud Walkers listed on various databases, but this is the first time I've read about it anywhere else. Unfortunately, like most of Jackie's television work, it doesn't seem to survive in any form (although if anyone knows differently, please get in touch).
If you'd like to read the full interview, it begins on this page.
Theatre Archive Project (archived homepage)
Archived interviews on Theatre Archive Project