The legalistic answer on this would be:
Sub 3″ folding non locking blade – legal to carry, no reasonable excuse needed*
all locking blades, or blades over 3″ – reasonable excuse needed (eg, I was going mountainbiking and needed it for cutting back branches etc.)
Leatherman – easy enough to claim reasonable excuse on the fact that you use the pliers/scissors/file for other uses, such as work/mountainbiking/cutting your toenails – this is unlikely to work when nicked outside a nightclub on a saturday night though.
* caveat – anything, including a sub 3″ bladed folding knife can be classified as an offensive weapon if the circumstances deem that a jury/magistrate thinks you were likely use it in such a fashion – eg hammer, cricket ball, newspaper (seriously!) Police officer would have no power to “confiscate” something without nicking you for suspected possession of offensive weapon/bladed article.