Hi LR1MICK, you say that you have engine oil to the cylinder head but nothing to the rockers. I am with Cobbadog in thinking you have a blockage. Some Lister engines had a restrictor wire inside the oil riser pipe to the cylinder head, this was to reduce the flow into the cylinder head. This wire can corrode and disintegrate into a rusty mess if you have had water contamination.
Let us know how you go,
Bob