This is one shrub which can be rejuvenated by stooling in winter, when its dormant, down as low as you like. You'll lose the flowers till it grows again though, otherwise, recommendation is to cut out some major stems to the ground and trim the rest.

Thanks Bamboo. Does "stooling" mean cutting down low? When you say rejuvenated, I hope that doesn't mean it will grow back even bigger?!

It should take some time to get that big again, and yes, stooling means very low down.

Agree with bamboo, always responds well to hard pruning.

Thanks very much . . . will wait a few months then.