Here's an answer I gave on hardy fuchsias in another question on Fuchsias asked recently

I grow perhaps 200 hundred hardy fuchsias from cuttings each year on my nursery. They are not very hardy when very small in their first year so I bring them indoors just before the first frosts and overwinter them in an unheated room in my home. They hang on in there over winter looking progressively more sad but can be potted on in late spring and planted out in late May/early June and they'll grow rapidly and should then be tough enough to survive the next winter outdoors although I usually mulch mine around the base of the plant to give some extra frost protection.

Another good tip is to plant the plants 2 inches deeper in the ground than they were in the pot as this gives more frost protection. Once the stems go woody adfter about a year they are quite hardy and although the top one thirdv of the shoots may be killed by the frosts these can be pruned off down to the ereging leaves after the frosts are over in late spring.

This is a one year old hardy fuchsia I took as a cutting and overwintered indoors and then planted into a bigger pot

http://www.flickr.com/photos/31559373@N00/4932826930

If your fuchsias are not hardy you'll need to over winter them indoors or in a heatyed greenhouse. I've been told that burying them outdoors to a depth of about 6 inches in a light soil or compost (mark with a stake) also works( dig them up again in May )but I've never tried it

I'm going to try this method this year

Have a look at Four Seasons site and work back from the wedding to when they took over an elderly neighbours garden where they overwinter some of their plants. There are visual and verbal hints and tips on how you might make a frost free zone for your tender plants. My perlargoniums and fuschias nearly all survived outdoors last winter in a close huddle of my big pots outdoors, under a double fleece tent, under a canopy. This year I only cut them back and fleeced them up in December at the start of that really bad weather. Result a fantastic long lasting colourful display of huge perlargoniums and 2 huge tender fuschias that survived the winter. As you have a greenhouse Four seasons is for you!