it is in pruning group 8 which means trim lightly after flowering and remove any branches that spoil the overall look of the shrub. remove any dead or diseased or damaged growth in mid spring.

So not that hard is what that means.. Having said that a neighbour cut one done from 5ft to 2 ft and it did regrow.

Yes agree, however don’t be afraid to hard prune or renovate them I have done this countless times over the years they always respond very well, if you intend to hard prune then you can do this after flowering or forgo this years flowering and do sooner, response time is fairly quick.

We've had one for 25 years and what a beauty it is.
I've cut it hard back twice during that time and I think it's time for another prune. They get very big don't they?

When I say hard back, I mean almost to the ground. Admittedly, I didn't know what I was doing the first time but I now have no qualms about cutting it hard back again.
It gets sun for about six hours at the start of the day.

Thanks for the info friends, ours is in the shade most of the year, my Mum says it is her bit of sunshine on grey days :o))
I do cut it back but it seems to grow back at twice the rate LOL. xx