Hi there
The 400D was/is a good camera, the only real difference is the screen on the back is a little smaller (2.5" rather than 3") and it is of course an 8mp rather than a 12mp (but still overkill for what most people need). The 450D has live view, which allows you to see things through the computer and the back of the camera, personally that doesn't bother me for normal photography as i prefer the view finder anyway.
There will be other minor differences, but to me the biggest one is money.
That 400D is £390, when a 450D with an 18-55mm lens is about
£500
But from Jessops if you buy a similar double lens kit, your paying
£640
I still think £390 for that eBay item is a good price for the camera, but you need to think, will you need a camera that good if it will be 99% product photography destined for the web at a max of 800 x 600 images.
The lenses are good enough for what anybody reading this thread including 99% of my photography will require. As the difference between these lenses and others that so called pros on photography forums talk about, is so small and almost un-noticeable, that unless your shouting for a fashion shoot, Magazine cover or a huge advertising campaign where it will be blown to bill board size at ultra high res it makes no difference.
So yes if you think you will use it for more than web-work, its a good deal, a good pair of lenses of different types to get you practising and seeing how it works, and also a battery grip which mainly make it look bigger than do anything functional.
I used my camera for time lapse (
like this movie i made here) last weekend, i drove all the way from Sunderland to Scarborough and back through the dales with the camera on a support in the car, taking over 8000 images at one per 3 seconds. I used one standard battery that comes with it (I had a spare one but didn't need it), so I'm not sure why people think they need an extra battery pack that holds 2 batteries or more, as you would need some MASSIVE photoshoot to kill a fully charged battery. Battery grips are more to make the camera look more substantial and impressive like the
1Ds MK3 which costs £6000 than anything functional. So next time you see a photographer with one, you now know the reason why, he is using a smaller cheaper end camera and wants it too look more impressive.
A true photographer plays with different cameras, right the way down to home made pin hole cameras, there are loads of forums and clubs around the
Lomo and
Holga cameras, which is basically a pin hole box, something like you would find in a cereal box. But some of the images are excellent, better than most people who buy Digital SLR cameras can produce. They have even given it a name,
Lomography
Sorry for rambling on, but I'm just trying to show the camera and lens really has very little to do with the photography, despite what a salesman from Jessops will tell you.