I think 7514 was also on the X21/22 today, but I'm not 100%.
7508 and 7529 both on the X14, though I'm not sure if they were both on all day. 7529 was sitting in Morpeth bus station this morning, around 11:40, before I saw it on the X14 around an hour later in Newcastle.
7439 was on the X10/X11.
4517 and 4662(?) were on the 43/44/45.
RE: Arriva North East: Rare & Odd Workings - June 2017