Now here's a long-shot at working out this frame..although I have never heard of the brand
There is a town in Lincolnshire, UK, called Bourne I think. I know that there was a family of cycle-shop owners/frame-builders called Bird who lived in Kent - there being both Alec, and Ken, who died unfortunately earlier this year. Perhaps there had been a father or a grandfather who had been in the trade in Lincolnshire at some time or other.
If you take the name Bird and attach it by a hyphen to the town Bourne, giving the term BIRD-BOURNE, it creates quite an attractive name that has quite a lightweight feel about it. Remember Bluemels "Featherweight" mudguards and pumps?
That's just about as far as I am prepared to push the bounds of incredulity tonight.
Norris Lockley...it must have been something I drank..Settle, UK