You are allowed to bring your own food and soft drinks into Winterville, but no alcohol. There are loads of bars on site serving everything from mulled wine to craft beers so you will be spoilt for choice once within the venue anyway.
Although I did see some people with their own food containers, most of the visitors chose to buy on site. Again, you have an endless amount of choices, everything from freshly prepared vegetable soups to churros, chillies and giant hot dogs. There are a host of street food vendors and plenty of seating under massive tents so you can stay dry and warm whilst you chomp away. Be prepared to spend within the region of £6-£10 on a burger/ bowl of chilli. The soups within the Fairy tent (kids zone) were a much more reasonable £3.50 per bowl.