I have a decision to make. I was going to go with the other publisher I mentioned. However through trade connections they've encountered a mainstream publisher who is currently accepting submissions and may well be interested.
As they put it, if I submit and it doesn't get picked up they will still be here and wanting to publish. If it does, then a publisher who actually works in the right field can do a lot more with it.
The back-up publisher still wants certain spin-off rights to do with their field, and I'd have no problems negotiating with them on that. They would benefit if it was picked up by a large company as it's more exposure for their spin-off.
The problem? Time. It takes months for a publisher to get back with a reply, and I am seriously not sure I want to wait when I have a route to publication open.
So I now currently have review requests, ongoing promotion, distribution channels, and interest in spin-off rights - and still no confirmed publisher.