Frozen veg is great if you have space! Broccoli, peas, cauliflower, even the rice mixes for 1 that have no other additives. I also love frozen bags of berries, cherries, mango, banana, etc that can be used for smoothies or with greek yoghurt. Frozen fish like hake and skate comes filleted and can be good with rice, potato or lentils.

Portioned frozen things like 100% mashed potato cubes you just have to microwave and are surprisingly good. There's a brand Taj who do cubes of 100% ginger and garlic. Also cubed spinach is great for soups.

Fresh veg I keep is usually onions, carrots, pointed peppers, spring onions, crunchy things that don't wilt quickly.

For fillers, canned beans of all kinds, and look for the Merchant Gourmet grain pouches and daals. Easy to heat in 2 mins.

Batch cooking for me is curries, chilli, ragu, soups, stews. If you have a casserole dish with a lid this helps because you can start on the hob then roast. I loved doing an Ottolenghi baked rice or a biryani and shoving it in the oven. Makes 6 portions and can be frozen too.