Yes, quite hard. Perhaps lose 30cm all over, and more on the width. Too much might shock it, but it looks healthy, so will probably respond well to a (careful) hard prune

If you want to cut it back more than that, try pruning back 1/3 of the longest branches this year, another third in 2014, and the remainder in 2015. That should allow you to eventually make it even smaller, without stressing the plant unduly.

WOW! I never knew Hydrangea could get so huge!

It's a lovely one, isn't it, and normally only as big when allowed to take over a shed, or wall.

Just a thought - if you cut off the forward facing branches perhaps it could be encouraged to spread sideways over the wall - that's what they do when they cover house fronts - they are potentially very big plants and normally self clinging. They sometimes need a bit of encouragement to start clinging on. Apologies of you knew all this!

Thank you all for your replies. Yes, it is a climber, and it clings to the wall very much so too. When the wall is due for a paint we can no longer ease it forward a bit to get the paint behind it, its clung on so well, so we have to sort of paint round it trying not to paint the leaves !!!

lol!