Im setting off at 5.30, and avoiding the m3 , m25 route, going up via a34 and m40 then accross, not sure as to what time ill get to m1 junction 15. If i recall, myself and steathwolf last year did 1.30hr from Wichester to those services. Which means if thats the case , ill be passing services between 7.15-7.30 ian if you want to be there earlier mate.
Up to you