Personally I am not nearly as interested in bestsellers these days as I used to be. Most of the books on the hot list end up there by virtue of (a) having been written by old hands or celebrities, and (b) an expensive publicity drive on the part of the publisher. Which is all very well and good, but it doesn't necessarily mean that the book is going to interest me.
However, if you are keen to know what the great British public was willing/persuaded to buy in 2005, booktrade.info has a link to a table in the Guardian which sets it all out. This is a pdf file which is considerably larger than A4. If you reduce it to fit on A4 you may need a magnifying glass.
Meanwhile, and also in the Guardian, Robert McCrum makes ten predictions about things which are pretty much certain to happen, mostly bookwise, in 2006. They seem fairly accurate to me.