Who do you call when you witness someone breaking the law
You mean this law? The one in your OP seems to suppose that the misleading has already been established and the issue has to do with the established misleader proving his misleading wasn't intentional.
Brians OP writes:
But under the EU Unfair Commercial Practices Directive the onus is now on the person providing the service to prove that they did not intentionally mislead their customers.
Imagine I'm the policeman you've called to the scene. Your holding the coin collecting perp by collar awaiting my arrival. You quote the law and say to me....
What precisely?