do you prune it in spring?
Don't do any pruning next year as the flowers form on this years wood for next summer. Give it a feed in spring as the new leaves open.

It looks like it is in a sheltered corner. Is it too dry there for it?

It looks very healthy so have you been feeding it, if so with what? Perhaps try feeding with a high potash fertiliser alone which will encourage flowering next year.

Hi all no I don't prune it I have just ordered a bag of Westland hydrangea feed for next spring. It's not really sheltered its just up against a fence and a plastic greenhouse the border is not too dry due to a water pipe which runs down the slope and leaks!
Thanks again