Thanks skytrain,
I have a feeling that it's likely to be in Walter's lovingly compiled book of around 6000 aircraft geeneral aviation aircraft, although it may be a tad early for that!
As for me, good old (some say) "Fright Archive", which, once you have an idea of the year and can do a one word search is pretty good!
air force | royal aero | aero club | 1949 | 0190 | Flight Archive
I see our late lamented friend William Green took the photo, so it's very likely to be in one of his books (if only I had some)!