Derek, u will need to remove both rear upper trims, rear upper central roof trim, & then u can gain access to the aerial grommet. It will also be easier if u remove the 2nd row grab handles in the roof, this lets the roof lining drop further, from memory there are 2 clips in the centre of the roof lining, u can remove these if needed, just gives u more room to play in.
Be careful the roof lining is fibre glass, gloves & mask is a good idea too.
Cheers