Yep, not working. Unwatched this thread soon after my last post above to test the theory, I woke up to this on my new replies page
Then don't click "Show new replies to your posts.", and use the Watchlist instead:
Oh... yet another feature of the forum I didn't know. Thanks for this, I'll start trying this and unwatch the old topics. If if works nicely, I might start changing habit and visit the watchlist page instead of the new replies