Sunderland reserve Volvo Olympian 16833 is being used on the 510 service today. I assume 16839 is being used as well.
ADL E400s 19194 and 19197 are providing extra capacity on the "E" services. Those are the only double decker's I've seen on the "E" services today.
RE: Stagecoach North East: Rare & Odd Workings - July 2015