Looks like 625-634 and 639 have now been withdrawn. I suspect 639 will be transferring to Go North West to join 637 and 638. As for the others, I can see them transferring to Go South Coast to replace older Solos (the oldest of which are nearly twice their age at 52 reg!)
As for 8305/6, both of those aren't withdrawn and are still tracking on Bustimes today. On the other hand, 8300/1 haven't been tracked since the 25th and 19th respectively, so it's possible that they've been withdrawn instead.
RE: Go North East: Withdrawn Vehicles & Fleet Disposals