I think you could do it for £60 as well.
If you need 3 meals a a day for 4 people, 2 of which are kids, and they eat like sparrows
Just a quick easy way to get it cheaper.
Having porridge for breakfast, sandwiches, fruit and yoghurt for lunch
Pasta/rice, cheap protein, veggies for dinner
Tea/coffee/squash to drink
Fruit for snacks
So
Breakfast
1kg of porridge for breakfast - 85p
12 pints of milk - £5
Lunch
2 loaves of bread - £1.10
Tub of spread - £1.25
Cheese - £2.59
Jam - 50p
Peanut butter - £1
Dinners
1kg rice - 95p
1kg pasta - 75p
2 tin tuna - £1.50
Chicken drumsticks - £2.15
4 x Tins of tomato - £1.30
Bag carrots - 50p
Onions - £1
Frozen sweetcorn, peas, mixed veg - £4.50
Mince - £3
Lentils - 90p
Frozen fish - £4
Fruit for snacks and porridge etc
Bananas x 2 bags £1.60
Apples x 12 - £2
Satsumas - £2
That's £40
So is still have £20 for even more. Could get a dozen eggs, toiletries, some crisps, some curry/pasta sauce mixes, more veg and fruit, tea/coffee, more pasta and rice, some yoghurt etc
It can be done, if you choose cheaper options. No one's living off £60 p/w eating avocado and poached eggs on organic sourdough toast with grass fed butter etc