I'd recommend either Canon or Nikon, they both offer very good scope in terms of range of lenses. I don't have direct experience of the 1000D but I've read reviews and it looks like an excellent starter SLR, I think the Nikon equivalent is the D3000 which again has had good reviews. You'll probably pick either of those up with a kit lens bundle for around £300-400. A step up from that the 450D is a very, very good camera and I think the Nikon equivalent is the D5000, with a kit lens or a bundle those are probably in the £500-600 range now. One big bonus of the D5000 is that you can take videos on it as well as photos, the Canon 500D also offers this but I think with a lens it may be out of your price range. Really any of these 'prosumer' DSLRs are going to give good results if they're used properly and have a decent lens on them, you won't go far wrong whichever one you go for. For me it's the lens that really makes the difference, I'd rather have a slightly cheaper camera body and a really good lens than vice versa.
If you can find a good quality second hand model you could also consider the Canon 400D, it's a great camera and if you get a good deal on it you could put the rest of the money towards a good lens.
If you have a camera shop near you I'd recommend going along and talking to them about what you're looking for and they should be able to point you in the right direction and let you try out a few models, look at the controls etc. so you can see which one you feel comfortable with.