Had a good look at the head gasket, the cylinder block and the cyclinder head to try and see what was going on, not helped by a coating of oil coming down through the head bolt holes, but think I could make out evidence of leakage between the edge of the cylinder and the water ways on number 4 cylinder at least. Car has done 125k, not remapped / tuned .... and other than the usual ... not abused ... maybe it was just time for it to go?