I am planning to install a new and larger drive, approx 36 sq mts as my drive is on a bit of a slope is it wise to use 450 x450 x35 cm slabs. Also should they be dry jointed or wet mortar jointed.
Uh-oh! 35mm slabs/flags are only suitable for patios, Frank. they'll snap like wafers on a driveway unless they are laid on a full bed of C20 concrete.
Have a read of the section about Small Element Paving, which is much better suited to driveways.