This is unbelivably easy. I brought the rubber seal from the link above last week (£4.95 inc postage).
- Firstly pull the rear interior light off, it just pulls out with fingernails.
-Then loosen the nut holding the aerial base. If you have the right spanner for this great, if not just use a standard pair of pliars. Once loose you can loosen it further by hand, but don't take it off, just loosen it until the end of the thread
- Now the aerial base will be loose from the roof and you can easily pull the old seal out without scraping around on the paint work.
- boil a kettle and put the new rubber seal in for a few mins (not whilst the water is still boling hot though)
- stretch the seal over the aerial base and position correctly
- tighten base nut from inside and push interior light back on