Not sure if my mind is playing tricks but wasn't there once a Stagecoach service that went from Sunderland to Boldon Asda (I'm thinking it was the 5 and it also went to/from Doxford Park Morrisons store entrance inside the car park) however I stand to be corrected.

Heworth to Sunderland by bus would be useful for when there is no Metro, I agree with that.