It looks like Jasmine or possibly a clematis. I favour the first but someone will know for sure.

One of the species clematis. Never sure which ones without looking a the Hull site.
http://www.clematis.hull.ac.uk/

Clematis connata I reckon, image here

http://www.joycreek.com/Clematis-connata-150-004.htm

Or clematis rehderiana (which has a scent)

Ah, that's the one I was thinking of, Andrew, but couldn't remember the name.