Thought I'd add a little update based on information I found out for myself today.
Tried to get into the Hyde Park Olympics Festival earlier on and they run it in exactly the same way as the sporting venues.
They weren't allowing any food or drink in, however you can take a bottle as there are actual water filling points inside. The Steward even recommended buying bottles of water from across the road & emptying/drinking it first, as its cheaper than buying one inside. Beer is also £5 a pint!
The other issue was to do with cameras...
Despite the rule they've mentioned in the official PDF about no cameras over 30cm in length, they were saying that cameras could not be over 6 inches in length, which is only 15cm!
I had a chat with a steward about it, as I had a my 70-200L and a couple of other lenses in my bag and wanted to know how serious they were about it, before I bothered trying to queue up to get in. She was totally honest and said that anything over 6 inches is banned, purely because they don't want anyone making money off photos when they aren't licensed to do so. So clearly anything that looks remotely professional isn't going to go down well.
I don't really post on Talk Photography but will be keeping an eye on that, maybe start a thread myself.