There are only 3 up LNER trains that call at Stevenage before 8.30am, and none are more than 7 coaches, so I can understand LNER's issue.
0704 (0500 ex Leeds, 225 set)
0750 (0609 ex York, 5-car bimode)
0803 (0605 ex Leeds, 225 set)
Incidentally, "nearly all" the Newcastle daytime services will not be 5-car - half of them will be. The evening services (1N33/34) are 9-car.
9-car: 1N01/02/04/06/08/09/12/15
5-car: 1N00/03/05/07/10/11/13/14
There does appear to be a spare 801/1 5-car unaccounted for, though, so one of the 5-cars could be a 10 (or of course it could work one of the Leeds diagrams instead of a 5).