Depends to some extent which one it is and when it flowers, I'm afraid. When you do prune, don't do it before spring, and most of them are very good at growing anew from near the base of stems, which means you can cut them back quite a bit.

...and use the bits for cuttings.

i prune hebe a lot, an i alway do it hte same way = prune after flower - wiht some, htis will meen prune in Febrary - this is no prob if you choosin flower shoot, but pinch of hte flowers - root in good mix of soil and sharp sand - 2 yeer ago i do 115 cutting of hte dark leef purple flower one - today i hav 115 shrubs 2ft high - yes, evry singal one took- an i hav never no it not to,mind you, bamboo may be corect-maybe i just luky

thanks for your replies, i've got a hebe sapphire if that means any thing? it flowered last year and had lovely purple flowers on it the flowers have now gone brown. shall i prune now or wait til march?? i also have two osteospermums that got killed off during the snow.... can i trim them back and hope for the best???

the hebe flowers in july!!

Yes, leave the pruning a little while longer. Also, trim back the Osteospermum in a couple of weeks when all this cold weather is gone. If they were the O. jucundum type then they are probably OK, but all the summer bedding types are a bit more tender.

thanxs volunteer