We went to the first one a few years ago, and just looked on the camp bestival website.
You have to pay to park, so if you haven't done this it's cheaper to do it in advance.
You can't take glass wear in, so plastic cups, mugs, bottles for water etc.
Food at any festival is expensive. When camping we've normally taken some fruit in a plastic box (to stop it getting bruised) ie apples, satsumas etc, and long life things like pieces of flapjack, small cartons of juice, dried fruit, oatcakes, nuts, jelly sweets.
If you're taking a camping stove there are designated areas you can use these in. Take pasta and sachets of pasta sauce for a quick, cheap and easy meal. Take plastic bowls and cutlery. Make sure you have the right size gas canister!
Wet wipes are your friend
Take enough nappies (and learn from my experience of having to buy nappies from an on site camping shop which were double the price of the supermarket)
Take a flask, and fill it with hot water in the morning to use later for hot drinks.
A bucket can be used as a washing up bowl, to carry things in from the car, and to store things in.
Use a shopping trolley instead of a bag for your clothes.
Wind up torches are useful and keep children entertained.
It can get cold at night, so take some thermal base layers and hats. Brightly coloured hats are easy to spot in a crowd.
Have a lovely time