...or even questioning the accuracy of the report "handed by US to UK
This is an old problem. The dossier is no doubt highly classified, which means CTOs and network designers can't question the accuracy. The dossier will probably be shared with GCHQ/CESG which is the government's trusted party to assess the accuracy and risks contained in the dossier.
Sometimes that's digested and then some parties are briefed. That's easiest inside government/public sector networks that have to be certified against government security standards.. But other network operators are generally left in the dark. For 5G deployment, given the national significance, I suspect the network leads will get briefed on the content, but those briefings will be classified.
For other potential Huawei users, well, use at your own risk. Which I think is a mistake, and the government/GCHQ should be more open with security advisories/best practice information given attacks against private commercial networks often have large economic impacts.