Edd,
are you referrring to mainly "dried" meals as I get the impression that you dont mind tins.
John West do a sachet of tuna - different flavours, so you have packaging but far lighter and more convenient than tins.
Sun dried tomatoes - not in oil again is a sachet or dried mushrooms etc- you can cut them up and put them with the the Tuna in pasta and a little bit of parmesan cheese.
Small amount of herbs and spices works wonder.
Also you can get small pepperoni ( about 2 inches long) that can be cut up
For rice, which can be a bit boring you can add flavouring to the water
Also, if you dont mind weight, and its only for a night or 2 , a number of people seem to like the Look at what we found meals- meatballs, hotpot and loads of others. You need something to bulk them out like couscous, rice or past but they are very tasty they are about £2
A very cheap and cheerful solution of dried potato () and add a cuppa soup to it, like a chicken and veg result is very nearly a leading brand of dried meal at a 10th of the cost. just play around with different combo and add stuff like cheese / herbs etc.I cant vouch for the nutritional or energy valuebut will fill youup