Granted a festival is a festival but it is also one that claims to be a premier event and sells tickets at over £20 each - punters have a right to expect a professional performance even if it is a less expensive event in the Manor Pav. If it was a sing-song in the local pub or at a small village festival and with tickets at £3 that would be different.
Equally, dancers paying £8 or £10 could reasonably expect the festival management to have some concern for their well-being and open side flaps in the Blackmore Gardens when the marquee began to become severely overheated. I had to almost shout at the people in charge this year, but it worked. If the marquee had been more than half full (which it rarely was) and if the weather had been warmer it would have become as insufferable as in past years.