I have a 450D, its not the camera thats expensive, its the lenses you'll need.
The 50mm 1.8 is a bargain (£50 when I got it), but thats more like 80mm on a traditional SLR.
For weddings you're going to need something quite wide angled - I have a Sigma 10-20mm which was just shy of £400 - total price soon racks up.
Like Biffo the Bear said, try ebay, its the only chance you'll have on that budget.
My 450D came with the EF-S 18-55 IS lense and, its, um, OK, but JUST ok... You're not going to wow anyone with it.
Don't fall into the trap of thinking you can just upgrade the lens in a few years, by then your camera would be out of date - like buying a 300D now.
You MIGHT be better off hiring the kit as and when you need it?