I don't suppose you know the varietal name of it? How tall does it get and does it have bare stems (no leaves either) about halfway down all the way down to the bottom? When did it start flowering (as in what month...)?

The large flowers and that you're in Yorkshire would, a bit of a guess, suggest it needs clematis type 2 pruning. The RHS website or the GOYpedia is good for details.
Might be a good idea to mix the pruning, cut some of the long stems just to control & shape & cut others right down to a first branch?

Thanks...its reached about six feet in height. I will take a look at the stems tomorrow yo see if there are leaves and report back. I think it started flowering last week in July.

If it started that late, its more likely a prune group 3 - which means it should be cut down to about 6-8 inches in January or at least by mid February. If they're not cut in this way, they get very tall, all the flowers at the top, and bare stems at the lower half.

Bamboo is probably right on type 3 then, that's later flowering than my type 2 in Manchester

Thanks again...will do that I did check the leaves today and there are some lower down just no flowers.