It looks like ARGYRANTHEMUM frutescens (Marguerite) Pruning depends on what you want and can do. If you cut it back now and leave it outside, it will probably be killed by frost. If you can move it into a greenhouse, you can trim it back. It is best pruned in Spring.

Thanks for your speedy reply! Unfortunately, I dont have a greenhouse. If I leave it alone do you think it will survive a winter outside?

Very sheltered spot and well drained...maybe where you live though definitely not if the winter is anything like last winter. The original species come from the Canary Isles.

Oh dear! I really must take more notice of what I am buying and not just go for something that I like the look of. Its all part of the learning process, I guess!! THank you both for your help

It may survive Janque - I have 2 suggestions:
Dont prune, I dont cut back my summer flowering plants very much as I believe they get some protection from frosts.
Also try protecting the crown with a mulch of soil based compost.

Thanks Drc - so there may be some chance of it surviving. I will leave it alone and protect it with some compost

Fingers crossed!