Rather than a propagator I would go for a thermostatically controlled propagating mat.

I call ours the 'electric blanket', insofar as it is a mat roughly 6' x 2' which we roll out on the staging. We put a roll of polystyrene insulating wallpaper under it, and black polythene bin bags over it. It will have room for loads of seed/cutting trays.

All right, it's quite a lot more expensive than the propagators mentioned above, (somewhere around £70) depending on the size of mat you buy, but wouldn't be without the one we have.

We do also have propagators, two windowsill types we bought from Woolworths very cheaply, but they are not thermostatically controlled, so, if you don't keep a close check on your plants, you could end up with cooked seedlings/cuttings. Believe the voice of experience!!

valmarg