Thanks for your reply Shelley.
I haven't read the article yet, so my question may be answered! If it is, I'm sorry for wasting your time.
I'm syncing 2do to iCloud. To save duplication into Reminders, I've turned syncing of that app off. If I use Reminders for the type of alert that better suits my needs, and I sync it so that it's on my iPad too, I'll have all my 2do entries in Reminders. Duplication. I use 2do quite a bit, so it has built up over time.
What would yr solution be to stop 2do items appearing in Reminders?