Weston on the Green is permanently active, so no NOTAM required.
Winch gliding sites are marked on the CAA maps and I think it that the same people that don't take that as a message to avoid those spots will be the same that, as you say, can not find a NOTAM.
I am baffled to read that anyone has chased an 'intruder' to get a registration. I agree with you that this is as unclever as the alleged 'offence'