Thanks for the compliment, Nigel, as flights of fancy are all that I have these days...no new tangible ideas..that is, if any idea can be tangible, which of course it cannot.
Regarding the bike shop in Collindale,Birds of Collindale, was, of course, very well known among clubmen, and the shop used to advertise regularly in "Cycling" in the 50s, as I recall. It would seem more than likely that the two other Birds, Alec and Ken, were related to Jim. There were other Birds involved in the cycling business, being the brothers who set up the Swallow company, somewhere in Essex, nor far from London in the 80s and then went off into deepest Wales some time later. They specialised in tandems, touring and developed a number of quality products such as heavy-duty hubs.
The likelihood of you meeting up with the owner of one of the small handful of Bird-Bourne frames is very remote..and then it is likely that the frame would have lost its transfers. Perhaps you should opt for the next best possibility and try to obtain sets of, or copies of, Birds of Collindale transfers. It's more than possible that some member of the V-CC will have such a frame..and maybe fellow List member Mike Butler might just be able to oblige
Norris Lockley...Settle UK...where November has just arrived today