Hi Richie,
I think everyone except the below 5 guys suffer a little with long irons, it is usually a result of trying to get the ball airbourne. If you play to 12 then you know it can be a mental block which causes a slight bit of tention. We all hit better shot if we have a light grip free of any tention.

Cure for me maybe for you.

Every friendly and after work knock you play start using your 3 and 4 iron of the tee on the shorter par 4s, it's difficult at first because you want to hit driver, but you will grow in confidence and distance the more you use your long irons. You then feel confident to hit of the deck in competitions.
P.S I carry a 7 wood instead of a 5 just incase the lie is to poor for a long iron.

Hope this helps

Ian.