What's wrong with my tomatoes?

[Curlykale]

I have grown my tomatoes the same way as I have for the past 2-3 years - started the seeds off in a heated propogator then moved them into small pots next to the south facing patio doors of my dining room. Usually by now I would have had to pot them on into bigger pots and my dining room would be a jungle but this year they are just pathetic. They have hardly grown at all and a lot of them look decidedly unhealthy. I have grown several different varieties so it can't be down to dud seeds. I wondered if it could be the compost? I just used a cheapo Wilkos one. Or could there be another reason? Could it be that it has just been so cold this year? I don't think I've done anything differently to previous years. And a second question; when can I risk moving them into the (unheated) greenhouse?

[darcyvuqua]

Mine have been in the unheated greenhouse for just over three weeks now really worried about them with this cold snap predicted

[WendyC]

It does sound like the compost. Is it worth trying to repot a couple with fresh compost removing as much of the old stuff as possible.