Buying food for yourself on £ 40 per calendar month must be hard and there must be so many repeated dishes and wasting nothing from yesterdays food, i am not saying it cant be done at all, but adding a whopping 50% it would make it easy for me.
Good luck if this is what you are wanting buying your own food, but i must admit there are certain foods i dont eat what Emma buys so maybe your partner dont like anything you buy too and the other way round.
Be interesting what your budget is for the household bills and everyday stuff, or again do you just buy and pay your own way in life .