How to prune overgrown Hebes

Nick, is it shaded where its growing?
There seems to be a tree growing above it which might put it into a lot of shade through the summer.
It looks reasonably healthy to me, some dont flower profusely, other varietys do.
Some hardly flower at all.

 

I agree with Pete and to be honest some of the ones that don't have great flowers more than makes up with their nice dense, evergreen, rounded balls alhough not all are green some come in a very lovely shade of greeny/blue ...whoops sorry guys didn't mean for that to sound rude but I have to admit it might sound a little painful the greeny/blue bit to you boys! lol :D Hel.xxx.