Handy things are a bit of dry bag material to use as a patch when a tyre starts to break (or just buy awesome tyres)
few chain links
cable ties
duct tape
small bottle of chain oil
puncture repair kit
tyre levers
pump
swiss army knife (get the one with sissors if you can) and/or leatherman
multi tool (such as alien II) or set of allen keys and a small adjustable spanner.
disposable latex gloves 20 for £1- are useful things to have, keeps your hands free of oil.
Some one mentioned to me, once you get near Tain [about 100 miles from JOG] there is nowhere to service a bike going north, don't know how true that is but 100 miles without a bike shop can't be good.