Just catching up on this forum and happened to see this...
I'm afraid I feel partially responsible for this. When I first started to take my husband to the festival I suggested he take a fabric conditioner bottle because I'd heard about it and getting to the toilets in the night can be tricky...etc., etc.
Well I've created a sodding monster and years later he even brings them on regular camping trips with us. I've told him to stop but won't. I've had to be very firm about him not peeing anywhere near a ground sheet.
Regarding banning plastic, I'm sure it's about plastic bottle sales within the festival, not bottles brought in by ticket holders.