I know you don't want to split the shopping but look around for places where you can get a sack of rice (not a huge sack, we get a 10kg one) e.g. a Chinese supermarket. We spend a tenner and it feels like it lasts forever, well worth going separately for this.
Make sure you've got flour, fat and perhaps UHT milk in small cartons (stores indefinitely) in so that you can make a basic white sauce and flavour it with cheese, mushrooms or just have it plain - very flexible. Delia Smith used to have a quick white sauce method - here it is
Eggs; scrambled egg on toast, omelettes with mushrooms or herbs (grow your own, thyme and chives are the toughest and most flexible) eggs mornay (one or two eggs each, hard boil them and make cheese sauce while they are boiling, peel eggs and cut in half, pour cheese sauce over the top), skint kedgeree (bulk out a tiny bit of fish and a load of rice with hardboiled eggs and a sliced tomato or two).
Buy loose fruit and veg, and maybe loose meat and cheese from the deli counter. Slightly painful having to pick it all out but you really don't have to get the amounts that your supermarket has decided to sell you at maximum profit. Get a little bit of mince and bulk it out with tins of chopped toms and a handful of lentils (I can't put more in as ds will pick lentils out individually if he knows they are there!). Get one slice of bacon per person. Get 100g of something rather than a kilo or whatever. Get the number of carrots you have actually planned to eat, rather than 2kg.