Twiggyis it possible to sleep at the venue under the tables?
No. They are pretty strict on this. The indoor camping thing is legit though. It gets booked up fast so you've got to be on teh shit to get in. As a further note to camping, it's indoor so no rain but they never turn the overhead lights off. So if you think you can just rock up with a sleeping bag and get some serious shut eye, forget it. One of those pop-up tents is fine though. Most people will lay their towel over the tent to further block out the light. Also good for drying it.
If you want to go full on fancy AF then do what the old hands do, bring a garden marquee, a folding bed, buy a lambs wool rug from ikea and glamp with your Balloonicorn slippers