Back in the days when I used to frequent festivals (2005), I came up with an ingenious (and not entirely legal) idea of how to get into Glastonbury without buying a ticket or scaling a wall. The idea is to sneak into the festival grounds under cover of night, before any/all of the perimeter fences are erected. What you'll need to do then, is hide. In a hole in the ground. A hole that will be your home until the first day of the festival.
Obviously you'll need to have prepared this hiding place in advance. And as this hole will need a roof, I suggest utilising some sort of prefabricated wooden box, or even a customised skip, with all equipment and supplies you'll need stored within. That way all you'll need to do is sneak in, dig the hole, plant the skip, and then carefully lay the turf back on top so your hiding place is well hidden.
Here is an intricately detailed schematic* which I drew as the idea came to me:
*You'll be forgiven for thinking that this looks like that scribblings of a 7 year-old with learning difficulties. I had originally intended to spend many weeks perfecting this design. However I was somewhat intoxicated at the time, and therefore the above 2 minute rendering is as far I got with this project before I got distracted by some shapes and bright colours.
Now clearly this is an almost-genius idea, but the smarter amongst you may have already thought of some potential flaws with it. The most obvious being that by not buying a ticket, and utilising this scheme, will you actually be saving any money?
Well I'm not so sure that you will. You'd have to arrive at Worthy Farm before the fences go up, which I understand happens at least 6 weeks before the festival starts. Are your really prepared to give up all this time and effort just to get into a music festival? Then there's the cost of skip hire for 2 months. Plus the extra materials needed to make it habitable (roof, water drainage system, air circulation, chemical toilet, etc). Then food supplies for 2 months. Then there's the cost/hassle of transporting the thing on a truck. Not to mention the expense of hiring a JCB digger for a night. Plus you'd need drivers for both vehicles to drive them back to remove any evidence.
On the other hand you wouldn't actually be paying any rent for the duration that you were there. How much money would that save you? ... So I don't know, perhaps it could be an economically sound plan.
But then there's always the risk factor to consider. I've got to be honest with you; there is a fair possibility of either prosecution or death.