Ok. Thanks for the help. I have solved the fan problem. I wired it to 2 6 volt batteries and gave it a switch and built it a plastic casing. It's all in fine working order.
I've decided to only set up the top shelf so far, so I'm looking for ways to heat. I have 28W of light already for the top shelf, so I just need to look for a little fluorescent light. Even 18W will bring it up past 40W. Which should be enough to start with germinating lowland seeds, shouldn't it? I will add more lately, but just temporary because once the seeds are ready I have to accept them, Nep seeds don't have a long shelf life!
I've found a way (I think) of succesfully heating it until I can find an affordable electronic heat pad. I was thinking about one of these things:http://www.mavco.co.nz/index.aspx?site=465&page=3979. The only thing is they don't last for more than an hour before they begin to cool down. However, maybe I could get around this somehow?