hi Nicky,
my only guess would be that the inner circle is infact the golden circle.. at the greenday gig there was only the golden circle so im guessing it will be the same layout.
http://www.thenationalbowl.net/
^ i found the official bowl site to be very helpful with facts & also the message boards are also good for any particular questions you want answering.
also another thing is it does say on the site that bottles (dont take glass) like water & juice bottles will be confiscated but we took a backpack and had about 4/5 bottles of juice and water in and we didnt have a problem, they didnt even look in our bags!
oh and if you get hungry dont worry there is every kind of food imagineable, not actually in the bowl, but just outside once you get through the gates there is a big part with lots of food sellers and stuff.
Theres also beer tents and most likely a merchandise stall once inside the bowl.
hope this helps :-)