I'm surprised that more hasn't been made of the header by Gelling. I know folk may say it's sour grapes to blame the defeat on that try (it did win Wire the game after all!), but I find it odd more hasn't been made of it. I checked on Rugby-League.com #RFL125 under Laws of The Game where it states:
Heading The Ball: It is illegal to head the ball in a forward direction.
There's no mention of "deliberate" or "accidental" unlike a knock on which is dealt with prior to the heading law. So the law is clear, intentional or not, it's illegal.