Yes, that's the procedure, but as I said, it doesn't hurt to get the manufacturer involved.
Usually they exchange whatever good is faulty without much fuss.
It's true that the request must come from the plumber, he has a contract of sale with Ideal, but if he's not prepared to do anything, the op needs to inform the manufacturer that he has been given a faulty product and is not prepared to accept a repair.
Also, one of the points of the pre-action conduct and protocol is to try and avoid taking people and companies to court.
Any judge would be asking why the op didn't contact the manufacturer which could've solved the problem without getting into a court of law.
Furthermore, the op needs to consider that the plumber could be penniless and/or operating under a limited company, so any judgement could be unsatisfied and the op would end up with nothing as well as court expenses.
I would definitely get Ideal involved.