In reply to johnboybuchan:
A) depends how dry is dry... if it's dusty and rocky then I've found Specialized and Maxxis tyres to be really good, and Michelin and Schwalbe to get cut up more easily.
Larsen TT/Crossmark/Fast Trak Control on the back and Ground Control/Captain Control/Ignitor on the front seem to be good combinations.
B) Mud? Can't help with that, sorry.