Thank you for all your replies.
I've had a read through GoMog....very informative, thanks.
Gonna run the car and check for leaks again, then with the cap off to see where coolant level rises too in tank.
When running engine with the pressure cap off don't let it start boiling or you will have a hell of a mess to clean up. Yes, there should be coolant up to the marker in the expansion tank when engine has cooled. Just a small amount of air in the system can adversely effect performance so always wise to have a good burp, the other watch point when replacing the engine thermostat is to make sure the air hole is at the 12 o'clock position.
