The only way Allan Campbell, or anyone else, will really know how far he can go, is by moving onwards and upwards now. He's nothing more to prove here and since you can hardly get a fag paper between most of the SPL, it should be England. Decent Championship side would be a great start, there's no way he's Premiership standard yet. I'd love to see him make it in time.
Whatever his true level turns out to be, managers will always love his attitude, so he should hopefully have a good career in front of him.