For a particular (suicide related) site I know that it was 'made known' to resi-ISPs here and as far as I know everyone with existing capability to do so blocke

For a particular (suicide related) site I know that it was 'made known' to resi-ISPs here and as far as I know everyone with existing capability to do so blocked it (though for some smaller ISPs just at the DNS level, so essentially superficially). Though that was just on the honour/good will system, I don't think any had to be forced. I think that essentially this is probably the best way to do it, IF we must go down this route (and I think in some cases we probably have to).