Freckles should be o.k. on a West facing fence. But if not have a look for one of the C. macropetalas, the American equivalent of C. alpina. The one we have flowers beautifully on a South facing wall. Its roots are well in shade though, under the path.

I have a winter flowering clematis 'cirrhosa' on a west-facing fence. It took a couple of years to really take off but it has the most wonderful nodding bells and they are freckly too, at the end of winter. I have just cut it hard back as it had grown too big so maybe too vigorous for your wants.

Thank you owdboggy and merlinbabydog. I will get a 'cirrhosa' as I really want some interest in the winter. Taylor clematis looks like a good supplier. It's on my 'to get' list!