Hello, linjarvis. The pictures were a bit fuzzy when I tried to enlarge them. I could not tell if it was a hydrangea or a vibirnum so I will mention some of the things I know about CH to see if what I say matches what you see. An Internet search for 'climbing hydrangea pictures' will give you many pictures and facts to see.
While there are several versions of hydrangea with the common name of "climbing hydrangea", THE one normally associated with the "climbing hydrangea" name is H. anomala subspecies petiolaris. It is a deciduous grower from areas in and around Japan that can be seen in many cold zones and in a multitude of ways. It can be superb once it gets to the top of the tree, the house wall, a telephone pole, fence or whatever object it climbs. Because it eventually can be heavy, you do not want to grow it in one of those wooden trellises. But it is also very persnickety and temperamental in that it acts like it refuses to produce lots of bloomage until it gets to the top of whatever it will eventually cover. So, it might bloom quicker up a fence than if climbing a tall tree. The roots cling like ivy and does well on limestone walls. It can grow 80 feet tall and more so very few things are not in its reach. Again, there are awesome pictures of it on the internet if you do a search. Its flowers are lacecap-like, produced in the summer time (vibirnums bloom earlier), with white sepals around the real fertile flowers. The sepals turn a shade of pink after the blooms mature. It prefers morning sun and afternoon shade but does well in bright shade or dappled sun. It does not seem to be picky of soil types. It has serrated leaves on opposite sides of green/brown stems with 1/2" to 4" long petioles.
Others... sometimes referred to as CH's "cousins": H. seemani does not have serrated leaves and, being from Mexico, it is not as cold hardy (Z8-9). Schizo, aka H. schizophragma has small serrated leaves and produces flowers earlier and is almost as hardy (Z5); one version has pink sepals.
