Thanks for the replies, but my other half has now ordered me the Canon 500d from his catalogue! So I'm really happy and excited about getting it in two weeks!
I will probably sell my Nikon D40, as although it takes fantastic pictures, the lenses for it are too expensive, plus the 500d has a bigger and better sensor. Also, I can't really justify having two SLRs. The 500d only comes with the 18-55 image stabilized lens, but as my other half also has a Canon 1000d, we'll be able to share lenses and the Canon lenses aren't as expensive.