Me and DH are vegetarian and we spend around £150 to £200 a month on food, toiletries etc.
As others have said, menu planning is the key. Also always take a list when you go shopping and stick to it or shop online.
We use loads of lentils, chickpeas and beans in our meals and buy them in large quantities as the small packs work out much dearer and don't last 5 minutes. If you have an indian supermarket near you that is the best place to buy them.
At the moment we are eating loads of stews and curries. Egg and lentil curry (Delia Smith recipe) is absolutely delicious and it's quick and easy to make and inexpensive I usually make at least 2 portions and freeze one.
Making double of meals and freezing half means you haven't got to cook from scratch when you get home from work. Also you could batch cook one day a week.
I soak big bowls of chickpeas, beans etc overnight then cook and freeze in portions in bags. Then when I want to use them I don't have to faff about with the soaking and cooking.
Lentils are cheap and you can make many meals with them - curries, shepherds pie, lasagne, bolognaise, chilli. Beans can also be used for meals like chilli or burgers.
Do you have a market near you that you can get to? Usually fruit and veg is cheaper than in supermarkets and if you go when they are packing up most of them sell things really cheaply.
You can use just veg to make things like chilli, shepherds pie, lasagne, pasta bake, curries, ratatouille, roasted veg, veg tart (roasted veg on puff pastry).
Look online for recipes.
I don't buy brand names for cleaning products. Own brand work just as well.