I've read all of the replies in this thread, and excuse me for generalising rather than going through each post individually.
Fitting panniers and mudguards is possible on all of the bikes that we're looking at. The real tradeoff that we are making by going for cyclo-cross is comfort. But, ultimately, we're three fit lads, and the tour is meant to be an adventure, a bit of discomfort is all part of it. We're covering 500(+) miles of cycling, and are taking our time (around 50 miles a day) so we feel that the comfort we can deal with. Obviously we are going to try out all bikes before we purchase, so if we feel that they are going to get uncomfortable quickly, then we will look for something more comfortable.
Crackle, thanks very much for your suggestions, and I completely agree with your logic, but, looking at the Dawes that you mentioned, how does that differ from the cyclo-cross bikes' geometry, I've put a picture of it next to the evans bike, and they both look very similar shape-wise, not that I know much about bike geometry.
The three of us are going to what is supposed to be a good second-hand bike shop this afternoon (bike workshop at the top of the Christmas steps for you Bristol folk) If there's a used tourer, at a good price, in my size, then I think that I'd probbaly go for it, as a money saving (along with the comfort of course) would tip me in favour of a tourer.
A quick question on size guys and girls, I'm 6' with a 34" inside leg, which, according to a few guides, puts me in 58/59/60cm frame territory. I'm assuming that I should go for the largest that I find comfortable, because a longer reach is preferable as I'd be less bent over, and thus it's easier to get air into my lungs. What do y'all think/ do you have any links to a decent guide on the topic?