I’ve been to Glastonbury three times and in a camper and have always used https://www.dgmotorhomes.co.uk and would recommend them. Depending on your location they might be a bit out of the way, but the campers are lovely and the service is great!
I have a Chromebook, so purchased a Chromecast for about £15 which connects to the TV via USB. Works flawlessly. No cables required between the Chromebook and TV. The Chromebook stays in the office whilst I enjoy the match sat on the sofa.
"other people complain of boredom, I dream about it longingly "...
Everything you have occupied yourself with in the last three days screams "boredom".
Imagine being in the position that the biggest thing you have to worry about is a mole tunnelling in a raised bed. The fact you spent 5 hours on the phone to complain that someone opened the gate to your garden is hilarious.
Re: the payment on your debit card which they are yet to take. If you contact your bank and tell them you have lost that card then they'll cancel it and you'll get a new card number. When the hotel try to charge the card it'll fail as it's no longer an active card.