Most hebes seem to break quite well from quite low down. If it was mine and I wasn't confident I'd cut back about half to a third of it to within about 6". When that's put out some nice strong growth then next year I'd do the rest. that way you wouldn't stress the plant too much. I gave up on a similar one I had (not this variety though) after a few years as it never looked like the ones in the catalogues!

Thanks for that Stera..I also have a straggly one. I only pinched the tips out. If it doesn't bush up this summer, I'll try your way!

or prune down 1/3 of the stems to the sort of height you want it to be at. then the remaining 2/3rds will grow as before and if the 1/3 don't resprout then the rest of the plant will be ok.

You could try SBG's method first to be on the safe side!