Thanks all for the comments - some good discussion on wheel size. I would personally favour a 29er and I guess if I did buy one for touring be it off the shelf or DIY I would probably look at getting a 36 hole wheel built for the rear.
Thanks for the links rifraf, some good and inspiring stuff. Like the Ogre by the way, how did the DIY build compare to buying the generic complete bike +/-?
I see Jamis do a Steel 29er which is fairly reasonable on price.