Hi Rick. I am a relative newbie myself so I won't presume to advise you on
what equipment to buy.
However, step one is to look at a review site (e.g. dpreview.com) and see what they say about various models. I would agree with the earlier post that you are probably looking between Sony, Nikon and Canon. Don't be afraid to go back a couple of years to the older models if you need to limit your expenditure while you are just getting going.
I also would suggest you go into a good camera shop (i.e. not a high street UK-brand-name shop, but a local new and second-hand camera shop that the pros and professors use) and ask to hold and try the different cameras that you feel might suit you. You mention the 450D (which is what I have BTW), but I bought it over the Nikon D-something or other, because the Nikon was too big and heavy for my smaller hands and it does what I need it to do within my budget. It may be the opposite for you.
Once you have seen a camera you like the look/feel/spec of, then see what price the shop will do it for. Ask them if they are expecting any 2nd hand gear in soonish. Then, google the online places that are often mentioned on this site (and any other photo forum place) e.g. camera price busters,
london camera exchange etc. and see what they have on offer new or 2nd hand. If you get it from a shop 2nd hand or refurbished then you should still get a bit of a warranty. If you are buying from a private individual then take the advice offered earlier and find out the number of shutter releases and aim for someone who contributes to a forum etc. as they are less likely to be out to con you. At your type of budget I would avoid the grey imports from that online bay of bargains as you're probably not going to be saving that much.
IMHO a new 450D with one kit lens for £470ish may be a bit expensive for a beginner, if that is your realistic starting budget. I don't know how much of a beginner to photography you are, but if you get going with photography then you will probably upgrade the body sooner rather than later, so consider the cheapest functional body of the brand that you want to go with. Older models can be vg value for money, which then gives you the funds left over to buy a
couple of different lenses (which you will carry over when you upgrade) and might enable you to hone your skills more extensively. The 450D new with more than one lens (plus spare battery, camera bag, tripod, photoshop programme, memory cards etc. etc) is probably closer to £700+. Although, you don't say what equipment you already have.
Consider perhaps waiting until after Xmas when all those people who got new cameras/lenses from Santa will be flocking

to offload their gear.
Edit -- Sorry, this thread has moved on a bit since I started my reply - and I see you have moved on to different things. However, my main point is not which camera is best e.g. 450D vs. 40D but which
range of kit you can realistically get for your skill level and budget.