Not sure as only done it once, but we got to the a27 turn off at hollingbury (coming from the west) at about 6.45 and we got to our seats as players walked out.
We did this for the Ajax game. Get there early because the queue was enormous and when you get there they tell you what car park but that’s it, you’ve got to find it yourself or follow the person in front And hope they were sent to the same car park