If you are over-nighting with a heavier pack, you are going to want a little heavier hiking boot as opposed to some trail-runner or light hiking shoe.
Something like that.
http://www.amazon.com/dp/B000XRE1T6/?tag=neogaf0e-20
As for food, your best bet is simply a system that can boil water. Here in the states we have these jet fuel things that can boil water in about a minute and you just dump it into a package of pre-cooked meals (can buy them at outdoor stores). Cliff bars and the de-hydrated food...those are going to be your lightest and best bets.
You sure your phone is going to work out there?
If you hop on the REI website and/or backpackers magainze, they have a bunch of checklists.
Off the top of my head.
backback. between 45-75L. If smaller, make sure plenty of straps to hook things on.
Tent: (which you have).
Sleeping Bag: (probably synthetic..drys out faster..especially if you are in Scotland)
Sleeping Mat: Essential, keeps you off the ground..The ground SUCKS the heat out of you. This leads to bad...bad things.
Way to boil water (IE cooking).
Water Filtration.
Camelback (3L) Maybe a Nalgene or two.
Food Enough for two days. (Think about 4000 calories).
First Aid (including blister stuff)
Head Lamp
Compression Sack to put one change of clothes (in case you fall in a river or something), can be used as a pillow.
I suggest a two day hike first. You will be AMAZED at how much you will learn on the first overnight. Then once you get your system down, hit up 3 days.