Pete W wrote:

http://www.sos.bangor.ac.uk/~oss108/cd175s.jpg

My guess: US spec, either TR7 or Jensen Healey. The clues have got to be in
the linkages and fuel line arrangement.

Aha! You're right, the linkage is the key.
It's an American spec TR5 (TR250) or TR6:
http://www.zeni.net/trf/TR6-250GC/24.php

Thanks everyone!