conducted by a TRE
That sir, is self-policing.
Did you hear about SSE taking a beating from Ofgem a couple of days ago? This former public, now private service was ripped apart for its selling practices that took place while they were being audited by people who stood to gain from the commission on sales!
Self-policing alone does not work for services to the public. There has to be some external assessment to back it up.