Just pulled off the rockers and pushrods and found a problem.
The rocker on No3 exhaust was loose. When rocker removed the exhaust pushrod came out with it. It seems the cup that the pushrod sits in has been pushed into the rocker arm, giving it the excess movement. Pushrod end is marked.
pictures of the rocker and pushrod
Is this a known problem with these rockers or am I just lucky!!