My suitcase food usually consists of tea bags, cereal, ham and super-noodles/pasta in sauce snacks. The first 3 ive always found to be expensive to buy out there and dont weigh much to carry, and pasta/noodles incase i fancy a snack before we go out somewhere. i have found proper butter (salted) out there but can't remember the name unfortunately...
The food out there is too nice to be taking half of tesco with me, everything tastes better and is always much fresher. I'm an extremely fussy eater but i have no problems stocking up..