Kevin,
I have to disagree regarding 'identikit' letters. Done in the traditional written way, they are more useful than a petition... the person concerned has a big pile of correspondence in their in-tray.
Done electronically, I don't know
Sending thousands of people the same email is easy, but sending one person the same email from thousands of different people is harder (I don't know of any software that allows you to do that - please post details)
Anyway, I'll write, concentrating on the fact that I won't go to Weymouth if this is the situation regarding live music