Done loads of this type of thing, long walks for charity etc. Keep tucking the food away, little and often and drink lots. The best thing I bought was a rucksack that holds a h2o bladder. Using that means the nozzle is never far from your mouth so you're always taking water on board. Some can't be arsed to stop and take a drink, but with a reservoir in your rucksack you can keep on moving and drink. Take snacks like jelly babies, Jaffa cakes etc for quick energy hits and when you've finished if you're not fecked, take some protein on board to aid recovery. Good luck. I've lost my nearest and d