The outward journey is (09:30) Queen Street to Waverley, then the 10:30 Edinburgh -> York (and I'm in coach G, seat 28). That was £17.50 as a GNER Standard Advance.
Back is the 13:10 Leeds -> York (Coach C, seat 63), then 14:06 York -> Edinburgh (Coach F, seat 35), then whenever from Waverley to Queen Street. It was £27 as a GNER Standard Advance.
Let me know how you get on...