Well, I picked up a cheapie compression tester from Ebay ($30 Aud delivered) amazingly cheap. Seems to work OK.
Results were 150 psi on all cylinders.
Importantly they were all the same, so, perhaps the leaky gasket is not telling me I need an engine rebuild.
As they say here:
As a rule, most engines should have 140 to 160 lbs. of cranking compression with no more than 10% difference between any of the cylinders.
Low compression in one cylinder usually indicates a bad exhaust valve. Low compression in two adjacent cylinders typically means you have a bad head gasket. Low compression in all cylinders would tell you the rings and cylinders are worn and the engine needs to be overhauled.
I will now locate the parts and tools to replace the head gasket.