5 weeks is enough don't worry. I do suggest getting SOME gear as it will make so much more possible easily. Here's a first suggestion with some prices seen on the forum.
- Radio triggers. RF-602 for example, £46 for transmitter + 2 receivers
- A second flashgun: YN-460-II flashguns are only £40 each. Yes £40, not £300 like the 580exII. Of course this is a fully MANUAL flash. But it's still great controllable light where you want it.
- 2 lightstands (tripods are too short for model shoot), let's say £30 total for 2.
- 2 foldable softboxes to put on the stands to diffuse the light, Flash In The Pan sells one with all the bits and bobs for £42 each, just put your radio trigger + flash on it and you're set
So that's about an even £200 for a 2 light set (your 580exII and the YN). This will allow you to do wonders especially if there's a good window in the room for a third light.
If you want to cut down on cost, the lightboxes can be replaced with umbrella adapters + umbrellas to shave off £50 or so and it will work in a white room where it doesn't matter that the light gets reflected by random surfaces.
If you cut it down to just your 580exII flash on a stand with an umbrella and ball adapter and the basic 1+1 wireless trigger set it'll be just £65 or so for the whole thing. Less than a nifty fifty
What you can do today is to learn how to use M (manual) mode on your camera. At some point in your flash learning, you'll want to go there anyway. Don't be afraid, it's fun. I just started with this stuff a week ago

If you want a specific effect, give us a URL and we'll tell you how it's done.