Looking at CR, I found a few makers that used that seat stay treatment. Here's a Bates B.A.R. that looks similar. http://www.classicrendezvous.com/Eve..._Seminar_5.htm

Here's a similar Ken Bird. http://www.classicrendezvous.com/Bri..._bike_1975.htm

Also MKM. http://www.classicrendezvous.com/Bri...km_T-Adams.htm

Bill Philbrook. http://www.classicrendezvous.com/Bri...ok_TTframe.htm

Charles Roberts. David Roberts road bike This looks the closest to your bike IMO.

It seems to be a fairly popular seat stay treatment with the British makers.