Had the same problem with mine, what a bl**dy awful job it was! don't fancy doing that again in the future, luckily my new Pirelli must have the later canbus, as it is fitted with the satnav unit already, phew!!
I remember it too me the best part of a day between everything, took a while to find it after firstly taking off wiper panel and hoping it was there!
Good luck anyway, sure you will get there in the end