Remove the parcel shelf from headlining - including sun visors, interior light etc. You will see a 10mm nut holding the aeriel base on - undo this. The aeriel will then 'POP' off by pulling it down(or go outside and pull the aeriel up from the top of the car.
DO NOT TWIST THE AERIEL BASE AS THER IS A LOCATOR ON AERIEL BASE(small plastic lug for locating it).
Refit in reverse - Good luck all!
RedfoxSteve, November 2012