you are being unrealistic to expect the 350d to be suddenly sold for peanuts just because the 400d is out. £450 is still very cheap for what is an excellent camera. I'd still go body only for £400 and spend more on a decent lens. There's no two ways about it, digital photography is an expensive hobby.
Wait till Photokina 2006 to see what Canon has in store, rumor has it an even lower end dSLR will be announced. Personally i'm waiting too see whether the 30D will be succeeded very soon or not before i grab one.