An update of the 1st video showing Vauxhall Insignia engine knocking. I decided to fit a new engine into the vehicle. In this video, old engine was stripped down to identify fault.

Faulty oil pickup seal resulting in low oil pressure.
This a common fault & effects the follow vehicles & engine codes...

Astra J 2010-16 - Engine code A20DTH, A20DTR, Y20DTJ & Z20DTJ
Cascada from 2013 - Engine code A20DTH& A20DTR
Insignia 2009-17 - All 2.0 Diesel Engines except Engine code B20DTH
Zafira C from 2012 - Engine Code A20DT, A20DTH, A20DTL, A20DTR, Y20DTJ & Z20DTJ

Replacement seal is readily available - Seal part number is GM 55589549