Please see pictures. This is becoming a common occurrence. After a run and then sitting coolant will sit in spark plug areas of cyl 1 & 2.
 
It kind of looks like it leaks down from thermostat housing but cyl 32spark plug is the one the that has most coolant in it and there is a rise in head casting between cyl 1 & 2 which with car stored on flat ground defeats logic if it were to come from thermostat housing.
 
How could it be getting there? Could head be porous or cracked?
 
Thanks,
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Head gasket leaking allowing coolant to leach up past the head bolt?

I would conduct a pressure test of the cooling system.
Hopefully this will show you where the coolant is coming from.
Good luck finding the leak.
Cheers
Craig

Thanks Paul and Craig.
I will check tension on head bolt but sounds like pressure test is the go.
 
RHys