we "camped" in boutique camping. mostly because, due to having to organise everyhitng else to the nth degree (dd1 is ASD), I couldn't face the camping and packing lists!
we did welll with food keeping. the girls are multiple food intolerant, so we always have to self cater.
I pre-froze ltos, which obvioulsy de-frosted over the weekend and was used. also, bung the frozen stuff, along with ice paks in a cool bag, and put the cool bag inside a coolbox. worked well for us, and we had food right up until sunday evening.
we don't use milk, so can't help you there, I'm afraid (although, surely UHT would be ok, if not actually cold? you could get the smaller cartons and use one a day?)
we took our P&T buggy - both dds now refuse to get in (6 and 3!) but it was useful for ferrying all the stuff around - blankets/juice/wipes etc. next year we will take our cycle trailer to do similar.
we loved it all - the girls were entranced, and dd1 got to meet her beloved Mr Tumble, so she was over the moon. dd2 braved the helter skelter (usually a scaredy cat) and loved it!
the weekend was all about the girls, really, and we didn't get to see much music, but heard it all anyway. was a great atmoshpere, and agree - there was so much more we could have done, given enough time!