agree with all suggestions on here..
macaroni cheese is cheep and yummy... cheaper if it becomes a value pasta (rather than actualy macaroni) with sheese sauce.... bu a cheap strong cheese so you dont need as much for the same taste.
also do you have people near by giving away apples from their garden? (round there there are loads)
My grandmother has a really yummy pork and apple casserole, with diced pork, and there was a big pack of diced pork reduced in asda today for a £1 which reminded of me of this recipie... combine that with some apples given away free from someons garden and you have 2 big meals for basicaly £1!
Can you go to lidl? they really have some bargains and some of quite alot of their stuff is actually really good!
Porridege for breakfast
sandwhiches / jack pots for lunch (get a big value sack of pots, there will be plenaty big ones for jackets and the smaellr ones can make mash to go on top of a cottage pie. etc
1 chicken can do loats of meals... roast it,
then use the some of the left over meat to make a chicken pie, then use the last bit to turn into chicken soup... with loads of cheep root veg! and serve with bread and butter
bulk out mince for bolognese etc with pulses and beg (I always whizz a whole onion 3 carrots, a courgette and normally a pepper too into a 'normal' size pack of mince befiore adding tomatos etc and i get enough bolognese to feed me, my 5 and 2 year old charges (who both have big appetites) for 3 meals! you could also add a tin of baked beans in to stretch it out even further!