Even with the benefit of a green house over wintering plants can still have its problems, a common one being Grey Mould. This is a disease which thrives in damp conditions combined with poor air circulation, a common combination in wet dank winter months. Tips to avoid grey mould are not to pack the plants in too tightly into the green house or cold frame and ventilate as much as possible. On mild days open up the doors and vents to improve air flow. A good idea is to raise the plant off  the ground which has two advantages. Its avoids the plant being on the very cold ground during periods of severe weather but also keeps the air flow underneath the plant as well. To raise the plant it's really easy to make some low trestle  or supports using couple of old bricks and a plant as shown in the photo here.

As much air flow as possible to prevent the grey mould and if you do spot it remove leaves, clean up around the plant and if  it had taken a hold with the plant remove it so prevent infection to the other plants.

Saving seed is a great way to raise new plants in the spring, but some seed is easier to find and save. On the left, Calendula, the English Marigold delightfully unattractive to slugs and as such very different to the popular, but ever eaten, French Marigold. If you have one Calendula, you will have a lifetimes supply. The seed is quite large and easy to handle; it dries well and sows reliably. Viola seed is also quite  easy, although much tricker to handle, you need to wait until the flower dies back creating the seed pod and just as it opens and ripens, harvest the seed. Rocket seed is easy as it runs to seed so easily.

But other seeds are rarer or more tricky and if you can't find what you want in the local garden centre, subscribing to the RHS seed scheme is a good source of buying unsual seed and easy time spent over the winter reading through the  catalogue  and looking up some of the less well know varieties and choosing some seeds for the spring.  You need to be a member of the RHS but its a great organisation, free entry to some gardens, the seed scheme, members advice area on the web site, and the monthly magazine is a gardening Magazine to beat all gardening mags.  

If you don't like green chutney and who does, you will need to ripen the tomatoes.

As the nights draw in there can be, depending on the summer weather,  a lot of green tomatoes on the plants. Two tips: firstly the greenhouse by this stage can be a tricky growing environment damp and prone to disease. Be bold and cut off many leaves to ensure as much air circulation as possible, check carefully for diseased leaves and cut these off. Ventilate the green house on mild days and avoid over watering as it will not evaporate as easily as in the summer months.  This will give the best chance of producing good fruit.

To ripen, cut the vines and bring into a warm place, such as a conservatory, or sunny window sill and the tomatoes will ripen. This really does work as one year when moving house it was necessary to cut all the vines and 90% subsequently ripened in a warm sunny spot.