Yeah the head was skimmed, had to remove the head though after initial fitting due to snapping a pencil in the fist cylinder like an idiot. However the engine was never run the first time so the gasket should have been fine.
how on earth did you end up with a pencil in your engine? anyway I would try retorqued the head bolts first just for the ell of it. start from the middle bolts. crack each 1 off slightly then retorque working your way outwards 1 at a time. not a guaranteed cure. but worth a shot.