Hmm, odd indeed. In a decade of working with them, it is exceedingly rare that I had to wait more than an hour for a reply.
I saw it mentioned a few times that this wasn't your IP space, but it was being leased to you? Makes one wonder if the IP space was already dirty, or had past issues, and you're inheriting that mess as well. Keep in mind that there several notorious companies using 'front' names to sell to spammers and avoid getting themselves dirty (
ColoCrossing->Velocity is a very good example of this;
DirectSpace is another example). I bring them up just to point out that Spamhaus has to deal with "we didn't know it was a spammer - really" excuse pretty regularly, and it's very possible that they're trying to dig deeper to see what's really going on.
Selling IP blocks isn't helping you either - looking at those SBLs, all the IPs are sequential. All it's going to take is a single spammer to make it look like you knowingly resell blocks to shady folks. Also worth keeping in mind that the listing is for SingleHop directly - Spamhaus may be expecting them to get involved, since the IP space is in their name. It's worth getting with SingleHop directly, explaining to them all the steps you've taken, and asking them to step forward as well. If they do, it'll likely help out a great deal. And if they refuse? You have no reason to stay with them anyway.
Folks are right though - you need your own IP space. Then even if you have to deal with persistent SBLs, you won't be getting eviction notices over it.
