Hi, bits of help only I'm afraid, I had two post war bikes with that bottom bracket, so I would guess late 40's. After the war there was still plenty of pre war frame fittings, even in the Brown brothers catalogues of the late 40's, you could still buy fittings that look pre war. It is a lovely frame, I will keep my eye open, but there's bits of numerous styles in the lugs - Claud butler classique lugs, spearpoints similar to some pre war R O Harrison, but its not a R O, the twin plate fork is similar my late 40's Stokes of London ( same Bottom Bracket by the way ), so it could be a long journey, the position of serial number may help ( is the number on the forks ? ) - keep digging and good luck. Terry