So i just tested with a couple of new rental discs - once again just 1080p Blu Ray rather than UHD - and my old Pioneer S12 worked a treat. This was after cleaning AND changing the enclosure to the vantec model from the OWC.
Not sure which one of the actions helped. I am expecting some UHD discs in the week so hopefully that would be OK.
I was slightly concerned as even he cleaning disc was skipping but what ever it was, seems to be working. Will keep the Verbatim handy for now but if not needed i can return it with a few weeks.
Thanks All for your help as always.