We are trying to cut back but it's hard when the dd's and dh are quite fussy. We have cut down on meat ( maybe have it once or twice a week ), I bought a side of salmon last week from Tescos for £13 and cut into 10 portions ( worked out much cheaper than buying small fillets ), buy a whole chicken and portion it out into breasts, legs, thighs and use the rest for soup, again much cheaper than buying the individual breasts and it can last for a couple meals.
I make 'baked bean lasagne' using a tin of beans, a tin of tomatoes , onion, bacon off cuts, pasta sheets and topped with cheese ( it's like a fried breakfast in a lasagne ), doesn't cost much to make and is very filling.
We also eat a lot of jacket potatoes and I make a big homemade pizza once a week, if I'm feeling lazy I make pizza with cheap pitta breads for the dd's.
Buy a sack of potatoes ( for mash, jackets, home made chips/wedges ).
I do spend around £50 a month on pet food for 2 dogs and a cat, sadly I can't do it much cheaper due to their diet needs.