One of the problems of getting a lot of your ideas about what plants are worth growing from books rather than seeing them in the flesh is that you sometimes totally misinterpret the scale. I'd assumed that this species was of much the same general look as other climbing hydrangeas. What i wasn't prepared for when i saw it at Wakehurst was that everything about it was several times the size of it's relatives. Those leaves are big leathery things about 6-8ins long. Extraordinary. In general, I'd recommend Schizophragma (either species - integrifolia or hydrangeoides) over Hydrangea petiolaris where a climbing hydrangea is required.