I probably should have included the X12/X13 in my list too, since they are South of Tyne, I guess. They were Sunderland to Doxford Park express services (housing estate, not the business park as it didn't exist then) which eventually evolved into the 12/13 in the post deregulation area.

I'm pretty sure there was a X14 which ran alongside them at some point between Sunderland and Moorside.