Neil,
I looked here and can't find it, but for general seed sowing there's an excellent FAQ at gardenweb that several of us were involved with writing. So you get lots of folks ideas/opinions all in one place.
Suze put the link here somewhere, but I can't find it. And I could go and get those links for you but it's a pain b'c I'm on AOL and have to minimize it to go to IE to get here and I'm just not up to it.
So go to gardenweb.com and on the Home page look for the Growing Tomatoes Forum. When you get there look at the top of the first page for the blue FAQ link. When you get to the FAQ's you'll find the seed starting one, a good one on cross pollination, another new one of leaf forms and another one on blossom end rot. Don't pay attention to the list of varieties one b'c it's way out of date.
You can read at GW but if you want to post you have to register, which is no big deal.
So I really think it would be good to read that seed starting FAQ first.
Speaking for my self, I hate what I think you're calling Jiffy pellets.