Top tip: buy bulk frozen meat and frozen vegetables. Any fresh vegetables buy from a market or something; not a supermarket. Their profit margins are ludicrous.
£52 is plenty, I managed £40 just fine. Don't go food shopping when you're hungry and always go for basics ranges etc. I managed on £15-20 food budget per week and I buy a heck of a lot of meat etc. (which is expensive).
Also, should go without saying but make sure you actually stick to your budget or you will be ****ed later in the year.