Peter Hale has forwarded me this extract from Cartoonland, a 1949 documentary about Anson Dyer and his studio, asking for help in identifying the artists shown in the film. The man in the first of the photos below is Harold Whitaker; if anyone recognises the rest, let me know.
Len Kirley, Laurie Price, John Garling, Tony Guy, Sid Griffiths, Bob Privett, Vic Bevis, Betty Smith and Mollie Zambra are all candidates.
Ronnie Rabbit by T. Payten Gunton and Frank Rogers, published in 1949 - possibly the inspiration for the animated character.
However, there does not appear to be any kind of record of a cartoon called Ronnie Rabbit ever being released. It may be that the footage was commissioned specifically for the documentary and the entire scenario staged, but this itself raises questions - for one, the clip of animation is not shown in its final state, only as a pencil test followed by individual cels.