That's a lot! But I guess it depends on your lifestyle. With kids, pets, and if you include toiletries, you might also include some homeware and ocassionally clothes if you're browsing those aisles, it's also possible to get stuck down the books & DVD sections...
Strictly food, I budget at £160 (2 adults) a month, but currently come in way under ~£100pm because the other adult doesn't always eat at home, and has had very few meals here recently.
I despise food waste so I often do "cupboard shops" rather than go to the shops, to use up anything that might be nearing the end of its life. I have a lot of vegetable based meals too, I don't always have meat.
Last week, the only item of food that didn't manage to make it into a breakfast, lunch, dinner, side dish or snack was half a broccoli that went yellow before I could use it. That was the only wasted food.
I think being more conscious of what you're bringing in helps. Of course, that does mean relying on the people you live with to be organised and let you know what they're doing so you can plan around everyone. The only time I ever have big waste (for ex. throwing out a pack of gone off meat) is if I've consciously planned to use something on a certain day and then all of a sudden OH throws a spanner in the works and says plans have changed. Not the end of the world but does contribute to waste of food and money.
I make smaller portions these days too and have leftovers. Saves cooking the next day, means I'm eating and consuming less, and spending less.
Could you get your family on board to help you get organised and meal plan more efficiently, to have less uneaten leftovers and less uneaten food in the fridge by the end of the week?
I keep a good stock of oils, spices, and dairy products - all the bits to create a good basis for a meal but always aim to eat all my fresh stuff up, and try to aim to eat dry goods within a reasonable time frame so I don't have pulses, beans and grains languishly at the back of the cupboard if I don't plan to actually use them. More cupboard space, and more money in my pocket!
It's definitely hard to change how you consciously consume, it's an effort you have to get in to the habit of.
By the time our bins are emptied, some fortnights it's barely 1/4 full (others it's closer to half full). It's noticably reduced drastically.