My arrival time in York is currently a bit undetermined, I've got no idea how busy the M25 is going to be on a Friday (fairly busy is my current thinking). I'm going to have to drive from Croydon haf way around the M25, up the M1, the A1(M) and then off the A64 towards York.
Google Maps reckons 4 hours 20 minutes, which I don't believe for a minute. Theoretically that would mean I could leave Croydon at 7-30 and still get to York on time, but somehow I think that would be pushing my luck!