Posted: 05/05/2014 at 11:59
Jon, Old compost for seeds is a no-no, seed compost needs to be sterile and old stuff will not be. I have used old compost though steamed it first or at least put it in a bucket and poured boiling water on it, a last minute fix not really recommended.
Seeds need a constant temperature very hard to control without a place to keep an eye on them it varies from 8C to 20 C depends on the seed though most veg will be the lower temperature, they will grow in outside seed beds although not until June in this area the Northeast Ne'er cast a clout till May is out is a truism up here.
Seeds will germinate in sand though my mix is one third sand one third grit and one third sterile compost then at two true leaves pot on to half compost half sand and grit mix, like babies they need to be weaned onto hard food, the old compost could be too rich.
If you have a South facing brick wall that will take in the heat and give it back at night then put your seed trays in a box next to the wall and cover with some rain proof material, you will need to open and close the lid according to temperature.
Without a greenhouse or an inside windowsill it is hard work and as with all gardening worth it in the end. Hope this helps.