Hi Andrew

I am with Alan.
What is the oil pressure at idle when cold?

What is the oil pressure at idle when warm/hot, when the light is on?

'oil light is not on when vehicle is cold just when warm'

I think this will be due to the thickness of the oil when the engine is warm.

The excessive clearence on the big end and main bearings will cause more of an issue when the oil is thinner.

hth
James