If the new 22:30 is booked to go via Welwyn, not Hertford, then it would be the same times as the current 22:00 at Peterborough, Grantham, Newark, and Doncaster. It's not yet clear if there will be a connection* from Leeds to York. If not, my last train back will be 21:00!From this December the 23:30 Kings Cross - Leeds will cease to run and the 22:00 Kings Cross - Newcastle will become the 22:30 and diverted to and terminate at Leeds. The 04:35 Newcastle - Kings Cross will start from York at 06:00.
These changes are supposed to have been imposed by SRA/DfT and Network Rail as to allow more time for overnight possessions.
* By that I mean a proper connection, I can't be doing with post-midnight hour long waits at Leeds!