Anyway, cleaned up now (was harder than it should have been) and some more antispam protection in place. I was overseas at the time so missed the big hit - apologies for those whose eyes are still bleeding from seeing all of those Porn links. Some private spam messages got out too which was annoying.
On the good side... apparently people are still actually using this forum and aren't spending all their days on facebook, so that is good to know!
Thanks to those who told me about the spam hit.