There is no definitive answer - when I had my mark 3 and 4, I never experienced any problems starting after flat battery or battery changeover - however from Time to time I have come across articles where some of the mark 2 s and 3 s have been fitted with an aftermarket scorpion alarm system which does need resetting - I would just put the battery back and give it a try and see what happens - I reckon it will just start as normal.