Firstly, I don't work at KGX but work on TL side so this may not be completely accurate.
The rest day pattern is a little random on the GN side but they work on average 4 days a week. You work two Saturdays in four, Sundays are up to you.
Routes are KGX - Cambridge/Peterbrough, Hertford Loop and Finsbury Park - Moorgate.
Of note, in October last year we were told KGX would be reducing from 114 to somewhere between 25 and 45 drivers. You are unlikely to get a position there or if you do, expect to get moved not long after you start!