If I need to do a pack-up, for whatever reason, mine tends to focus around protein and fat to keep my fuller longer.
A pack of chicken thighs (I think if I recall about 8 decent sized ones) is under £2 in Lidl. Cook them all at once (roasted, BBQ or airfried for me), then when cooled, wrap individually in foil and fridge what will be eating in a couple of days, then freeze the rest. As they are already foil wrapped, they are easy to remove from the freezer singly. If you are having them at work, if you take the out the night before, or in the morning, they'll have defrosted by the time you want to eat.
Wrapped in foil, they cane become (slightly inelegant) finger food. Wings or drummers also work, they they're less meaty.
Baby bell, or other little blocks of cheese. Again, if using block cheese, prepping ahead, wrapping cut mini-block portions in foil and refrigerating works well.
Cold meats - Buying a gammon joint from the butcher or supermarket, roasting, slicing and wrapping would be favoured by me, over processed ham.
A gammon hock, stripped of its skin (to be made into crackling), then boiled for stock, for soup, then the meat "pulled", by shredding with forks, then adding any condiments you like, like mayo, or chilli sauce, or whatever makes a great pot meal, eaten twith a fork.
A gammon hock in our butcher's in under £3 and gives crackling, a fair few sliced on the best parts, then plenty pulled gammon, plus soup stock. Leftover veggies, or a fridge clear up can go in the soup. All in all - loads of meals from under £3.
Oh, and of course hard boiled eggs.