Check the background service is running Mike. That's the one that actually turned reminders into emails. If it hasn't been running for a while, I'd turn outbound off for a bit, let background catch up and then decide if you want the queue oif emails to be sent out or to tidy them up.
Turns out that in my Reminder window, in the Analyst field..
I originally had CurrentAssignment\Analyst, i changed this to be Change\CurrentAssignment\Analyst.
seems to work now.