I think you should try building a course at home or somewhere really quiet where theres no other action and ignoring him when hes going mad. Only take him round when hes quiet and if he gets too manic just stop and wait for him to calm again. Slowly introduce a bit of action. I dont agree that the more he goes to shows the quieter he will become. Collies get a thrill from making things move, he may think that him barking is making everything move and he will never ever get bored of the thrill he gets. i.e dogs never get bored of barking at the postman do they? Also, little you can give him (treats etc) will ever compete with the high he gives himself.

If you can harness that enthusiasm you'll be pleased that hes belting round that fast.