Laneylop, I always start my toms off on the kitchen window cill. Just fill a small pot with multipurpose compost and sow your seeds and just put a plastic over it and you should soon see your seedlings coming through. When they a large enough to handle transplant them to small single pots and pop them into your greenhouse, they should be fine. Keep an eye on them to make sure they don't get too wet. Hope this helps.
Growing seedlings in a unheated greenhouse is fine, place seeds in good quality compost with fine covering. To speed up process either use plastic bag to cover of get a cheap propigator to protect from draughts until you have a couple of good strong leaves.
Can anyone give me some advice?
My tomato seedlings are about 3cm tall and now in separate pots- will they be alright in an unheated greenhouse when the night forecast is near freezing outside? Same for my aubergines and cougettes- I dont want to lose them all.
I found growing tomatoes from seed much better than buying the seedlings. Learning some of the best ways to grow from seed can help you benefit. I found this article very usful when starting mine.
How To Grow Tomatoes From Seed
I coulnt see a link there on that mushrom growing link Edd.
Should we start a new thread on the subject as this one's about tomatoes.