Most cyclocross bicycles have centrepull cantilever brakes (they are separated both sides of the wheel and have a small cable that the main cable pulls on-
http://www.sheldonbrown.com/cantilever-adjustment.html). This is because they don't clog with mud as much as other brake types. They are very similar to touring bicycles regarding the frame design/geometry (although cyclocross tend to get away with as light frame material as they can for the purpose) and there are clearances for larger/wider tyres like touring bikes. Cyclocross bike pretty much always have drop handlebars
A touring bike (lets say the Koga Miyata that Mark Beaumont used to cycle round the world with) are for very high mileage and are built for comfort, utility, low maintenance and are still quick enough to keep up a good pace. Touring bikes can have trekking bars or drop handlebars.
A straight bar road bike is what it says- a road bike frame/wheels/components but with a straight bar. These 'straight bar road bikes' are also called 'hybrid' bikes. To my knowledge they are the same and seem to be popular with people who prefer straight bars. BUT the drop and trekking handlebars you see on touring/racing bikes have more hand positions and will keep more comfortable on the ride you're wanting to do.
So I say, stay away from straight bar road bikes and go for the touring/cyclocross bicycle. You will get your different hand positions for comfort, the speed and the durability all-in-one with these bikes.
You could probably start off with a MTB with slicks but the geometry of the frame and gearing is still not built for the speed you want. You'll probably add another 15-20 mins with that kind of bike.
To be honest there are too many 'types' of bicycle now! I get confused about the differences as well and what i've said is to the best of my knowledge.
Sorry if what I've said sounds boring, it kind of is and the main thing is the FIT of the bike with you!
Good luck and keep us informed
Sam
ps check out the BBC info page of Mark Beaumont's kit!
http://www.bbc.co.uk/scotland/outdoo...ng_around/kit/