Looks like a clematis vitalba to me - native to the UK and known as Old Man's Beard, Traveller's Joy and so on. The leaves look right to me tho maybe a bit pale. Is this photo recent as it should be in flower from July to September and a bit later if it's mild?
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http://www.clematis.hull.ac.uk/new-clemdetail.cfm?dbkey=558
"We don't stop playing because we grow old; we grow old because we stop playing." - George Bernard Shaw