those O rings might be causing the leak,i presume they a green O rings?not sure if you have to take the cam out to fit them?i do not think so tho?

Remove cambelt then remove cam pulleys undo the 10mm bolt which was behind then pulley remove cam cover undo the 8mm nuts on the front cam caps remove caps,slide cam races out and you will see the O rings on the race housing!

Did you use sealant on the half moons?what cam cover gasket did you use?