Even without "proper" cooking, you can save a fortune on ready meals, tins, and packets, just by shopping around, and researching which supermarkets sell each thing cheaper than the others, look out for their offers, i.e. 3 for 2, clubcard discounts, or just temporary reductions. EG mccoys multipack crisps are always on offer somewhere between the main 3/4 supermarkets - if they're full price in Morrisons, they're probably half price in Tesco etc.
Just buy the non perishables (cans, packets, etc) when you see them on offer. Go to Aldi or Lidl for all the stuff that you don't want to be "big names", i.e. their own brand baked beans instead of Heinz etc. If you want to save money you have to be proactive.
Re the big stores for named items, do them in rotation, i.e. Morrisons on Monday, Tesco on Friday, Sainsbury the following Monday, etc. so you'll get the "offers/discounts" somewhere within a 10 day/2 week period.
Get all the store discount/club cards you can and use them - research what they offer and if you get extra points or a discount by buying, say, baked beans in Tesco, then buy your baked beans in Tesco with the club card - if there's no deal in Tesco but you can get extra Nectar points in Sainsbury for buying the same beans at the same price, buy them in Sainsbury. Even if you don't do online shopping, create online accounts with the main stores, and you can go online to see their offers/discounts from the comfort of your sofa, so you can plan your shopping lists to go to the store which has the best offers for what you need that week.
If all else fails, start getting into the habit of looking at the "short dated" area in the supermarket - even if you don't need it immediately, you can usually freeze to use subsequently. If you want to save money, you can't afford to be choosy and if there's several ready meal lasagnes at half price, then you need to buy a couple and either eat them or freeze them.
Also STOP doing interim "fill in" shops, especially stop going to smaller convenience stores, petrol stations, etc for the likes of bread and milk. You'll save a fortune by better planning so that you don't run out of stuff between "bigger" shops.
I think the OP could probably save 25% to 50% by buying virtually the same (i.e. no need to learn to cook etc) just by shopping around and taking advantage of the discounts/offers/loyalty cards, buying short dated items, not doing fill in shops, etc. All it takes is a bit of research and planning and flexibility. Obviously not ideal in terms of health and nutrition etc., but if short term finances are the aim, then it's a short term solution.
The op WILL be paying far more than she needs to do if she goes to the same shop all the time and isn't shopping around for deals/discounts - moreso if her "local" shop is a smaller convenience store (even if a big name). It's all a game to the supermarkets in cahoots with the main food manufacturers that they "rotate" the deals around the stores, so the more stores they go to, over say a month, the more they'll save over that month. Shoppers need to play it smart and play the stores at their own game by rotating and taking advantage of the deals.