Nutrition on the road - What, How and Why?

Looking for some ideas for the DD of what to take. At the moment I'm thinking some of everything along the sports food type shelf in evans or whatever and then some chorizos, a roll, crisps, flapjacks and just like a more normal food packed lunch to get away from weird gels and stuff I'm sure is packed with e numbers and chemical shit.

Also is there like an optimum time for eating before? I'm kinda hoping to have a lazy day with a sleep in the afternoon but make sure to drink plenty of water so when I start I'm well hydrated. Don't want to eat too late or too much or anything and give myself a crippling stitch or whatever the nice side effects could be.

I'm sure someone will make an obligatory "it will be fine" post but still.

for me 100 miles is: a pocket full of trail mix, some fruit and nut flapjack or oat biscuits (home-made, so no transfats/sugars) and a high five 4:1 water bottle.I eat a bowl of porridge with honey an hour before and something fatty and warm after.

that's not including water/ electrolyte drinks