What happened was that the HST's did the longer routes and then the WYPTE 321's did Leeds-London services and WAGN 317's did services to York and Newcastle.
Almost correct.
What happend after Sandy was the HSTs operated a 125mph service between Kings Cross and Newcastle, the obvious exceptions being those HSTs heading south from Aberdeen/Inverness.
Some 91s+MkIVs operated a 80mph service between Kings Cross and the north.
Northern Spirit provided stock to connect into these. A pair of 156s with NS and GNER crews did a couple of Newcastle-Edinburgh returns. Plus a 321/9 did a Leeds-London return.
Also a pair of WAGN 365s did a London-York return. This started out as a London-Leeds service, but en-route some one rememberd 365s wern't cleared for Doncaster-Leeds so they were sent to York instead.
No 317s were hired in on that day.
For the record, the photo of the 317s at Newcastle, it was a staff special for Hornesy depot staff.