My weekly bill today was £9.11 and included fruit (bananas and apples). Yeah, ok I do a "big shop" ever 4-5 weeks whereby that weeks bill is around £25-30 which is when I buy the main part of my evening meal (chicken, pork, beef) which I then split and freeze.
I would suggest (for a single person) that £20/week would be a minimum you could spend to cover breakfast, lunch and dinner and have it relatively balanced. I spent that for the month of November (£80) and a little more for the month of October (£100) which was a 5 week month (payday to payday).
I will leave it up to you to see if it is balanced:
Brekkie - Porridge with milk and sliced banana
Lunch - 4 x sandwiches with cheese/ham/salad leaves/salad cream + an apple
Dinner - Meat (pork, chicken, beef) with boiled potatoes and some frozen veg
I drink water with all meals which I get from the tap via a Brita filter jug or water machine at work
Do I eat like a king? Not at all but it is nice enough and includes fruit and veg daily.
Edit: I meant to add - I don't have any snacks or sweets/biscuits in the house. Sometimes I can be sat there and I feel like a bit of chocolate or a biscuit so it can be a pain at times but the OP never asked if it was good, just if it was possible