Ref,
you already produce a high standard of picture with whatever you are using. Let us know what that is please. Thing is that you can spend a bucket full of cash and get no better results. £600 will get you (almost) a new Nikon D80, should you want one - but you need a lens to bolt onto it and if you are after quality, then it does matter. Most of these cameras have specific modes built in to them and you can forget all of the above technospeak if you need to. In essence, you will get to know a new camera and soon start to associate certain settings with specific effects and it then becomes a natural and fun process. All of the camera "snobs" will have you believe that unless you are as smart, or experienced as they are, then you don't have a hope and this just is not true. Look back at your own photographs and ask if the investment is going to give you a quantative, or qualitative improvement over what you already achieve. If the answer is yes, then get ready to splash some cash - it will be worth it - and if you are ever in the BZN- Fairford area, then you are welcome to play with my own collection of odds and sods for a few hours, to see whether you feel better about your hunt for that elusive shot. You would be most welcome.
Conan