[Brakes] Intermittent Brake lights Berlingo Van 2012

[tigers1904]

Hi, Got a 2012 Berlingo van, Diesel 

Off side rear light comes on intermittently, if not on when I set off, I give it a quick tap and it comes on ??

Must be a lose connection in there I assume.

Does anyone know what the star size bolt is to remove the rear light cluster is? Imperial or Metric?

And is there any special ways of removal or just easy enough?

Many thanks for any information or replies in advance 

James