Removing tailgate light units? - 2006 A3 Sportback.

The lenses of high intensity and reversing light units in the tailgate have gone seriously cloudy over the years and I wish to polish them up. This would be far easier done with the lights removed, but I’m struggling to remove them.

I’ve removed the plastic trim covers in the tailgate and undone the 10mm nut, but the light unit doesn’t seem to want to come out, and forcing such things without understanding is a no no. I’ve seen a number of videos about how to change the bulbs, but nothing about how to remove the complete light unit.

Wondered if anyone has been there/done that, and can help? 
Many thanks and kind regards,

Gareth. 
p.s. I’m not referring to the sidelight/brake light/ indicator light unit in the rear quarters.