These were definetely in West Yorkshire on Airedale - Castleford routes as I used to have a weekly trip to town with my gran and vividly remember On The Buses on the bus
The advertising was a complete fail though as I remember absolutely nothing of adverts on them!
I also seem to recall that a few years ago Coastliner's route 840/843 Leeds-York-Scarborough/Whitby had TVs showing adverts for various visitor attractions along the route. Not sure if they still have them.