Who are the other ISPs who do not have filters?

There is no handy list that I know of.

The big six definitely do have the filters. Some smaller players do too, but a fair few don't. The only people I know for sure are A&A because they put their heads above the parapet and made a stand.

Some simply haven't implemented it because it would be work and they therefore won't until forced to (rather than because of any moral objection) - they'll not make any statement about not doing it as it will look bad if they eventually do.

There may of course be others in A&A's position who haven't done as good a job getting the message out.