A couple of thoughts, sorry if all of this is obvious...
Personally, I would be tempted to swap out the spare tarp for a poncho which can double up as either a windbreak, shelter, waterproof upper or even a sleeping bag cover.
I'd also use a midge lotion rather than a spray, takes up less space, gives more accurate coverage. Also if it's DEET based you can dab it on any ticks you pick up to encourage them to detach. I'd also strongly recommend you take up Angus Og's advice and get a midge headnet, you'll look like an idiot, but you'll be glad of it when all around you are screaming in frustration from the clouds of demonic beasties.
I've seen laminated versions of the WHW route map somewhere, you might want to think about that.
Also think about walking poles, they do make a big difference and you can use them to pitch your tarp if you find yourself having to make camp where there are no obvious trees or structures to tie off to.
Make sure you've got zinc oxide tape or Compeed plasters for blisters and blister-prevention in your FAK.
Aquaclear tabs are good, I think they taste foul though. Boiling water from clear, fast running sources is my preferred method. If you can get/afford a Pre-mac (there was a group buy touted on here late last year) they are very good too.
Oh and don't forget to pack some cordage, paracord or the like.
