Anyone had a go at tightening a loose rear roof aerial? Any idea what trim clips might be needed as roof lining must be removed me thinks?

You can gently pull down the rear edge of the roof lining and, depending upon what tools you have, can tighten the nut from there (22mm IIRC).

To make it easier you can remove the D-pillar trims as you'll then be less likely to damage the headlining.