There are two I managed to get working - neither is a mailing list, like uk-poly where everyone can email to the list.

That's certainly doable, but you either need to create a yahoogroup (or similar mailing list hosted by someone who wants to have ads) or be able to do more with your webhost. If that's a problem, ask me.

For a mailing list, it's considered essential that they join the list themselves, rather than you join them.

For an announcment list, where you can email everyone but they can't, it's less essential - and one of the announcements can be 'join the mailing list at...'

Sending to lots of people via To: or CC: is considered Bad. Or did I misunderstand that and you can't work out how to BCC: them? What email program are you using?

Are you coming to BiFest? If so, grab me for a chat about this.