If they're not already indoors, or in a greenhouse, Lainy, they're probably goners, sorry. You needed to bring them into shelter before it got very cold. I have had marguerites that survived a light frost, but not freezing conditions for days at a time, like we've had so far this year.

If you got them under cover before winter arrived - early this year - keep them frost free, water sparingly, and wait for spring before you harden them off and plant out when the risk of frost is over.

My Marguerites are really hardy and survive the cold well, they even stay evergreen and spread like mad, the plant I have is over 27 years old, from my Nan, are we talking about the same plant do you think?????

I have two outside that I'm not expecting to grow again next year Grandmage - I was caught out by early frost and they're looking "well dead". We lost the two I had last year - one was new that year and the other had come through a couple of milder winters. I'd be pleased to be wrong about mine - they were lovely! Perhaps yours are in a very sheltered spot?

My garden faces North so I tend to lose things at the drop of a hat but not my Marguerites, they are in a very open border!!! You never know do you!

Marguerite, or Paris Daisy, formerly in the genus Chrysanthemum, but now Argyranthemum frutescens. It's a somewhat frost tender, short-lived, shrubby perennial. They sometimes get frost damage even here in the subtropics, so I doubt that they will survive a winter in London. Unlike most members of the former Chrysanthemums, it never spreads by offsets, so I suspect your "Marguerites" are actually something else, Grandmage.

Wikipedia tells me that there are two species that can be called "Marguerite". One is Argyranthemum frutescens and the other is Leucanthemum vulgare or Chrysanthemum leucanthemum. The latter is also known as Ox-eye Daisy or Dog Daisy. I have lots of these and they're irrepressible!

Not sure which mine are as they are so old, some folks call them Shasta, is that right? My dear old Nan called them Marguerites and yes you are all right they are thugs, take a look at my photos to see my border picture maybe you could identify them for me, thanks so much.

Shasta daisies are related to Ox-eye daisies. Their latin name is Leucanthemum x superbum - they tend to be bigger than Ox-eye, but are just as tough. Marguerites are a lot daintier than these, but they're all daisy shaped flowers.

Is this the photo you meant?
http://www.growsonyou.com/photo/slideshow/164903-butterfly-on-the-daisies/member/grandmage

The size isn't clear, and I can't see the leaves - not that that would help a whole lot! :-)
If the flowers are 2" or more in diameter I'd say they're Shasta daisies, less and I'd call them Ox-eye. Both plants have a strange smell - not all that pleasant.

Beattie, the flowers are a good three inches I'd say and they are tough as old boots, even after the snow we have just had my plants are looking quite strong! Thanks for all the info.

I'll have to remember that Leucanthemum vulgare can also be called Marguerite. They're not so much thugs here, because they rarely survive the summer, but they do self-sow. Shastas are better at surviving the summer, but spread slowly, in my experience.