The UK absolutely and fundamentally should trust the US over China -- after all, the UK and the USA have no-holds-barred sharing of intelligence and spying, while the UK and China have literally no pact at all and are adversarial in that regard.
USA equipment would be orders of magnitude more safe for the British people, as by forming a pact with the US, the US has responsibility to the British government for the intelligence gathered (and vice versa on the mass amounts they collect on us through GCHQ!)
But to pretend that the US is guilty and the UK innocent is absolutely, egregious biased and false. They dragnet over 200 fiber interconnects and literally copy all internet traffic for analysis. They are not our victims, they are our brothers in arms. Don't forget that!
Well this is highest-level political commentary. Let's ignore the wars the US and UK fought against each other, and the times they allied with other countries. That one time the US and USSR fought a war together made them BFFs too...
The relationship is somewhat akin to ancient Greece and Rome, but closer.
With that said, I don't want anyone copying all internet traffic and sharing it with intelligence agencies. Of course, if I had to pick, I think I'd prefer it to be Uncle Sam doing it, but I fear the U.S. Government for drastically different reasons than I do China, in that the Chinese government is highly unlikely to be a threat to my basic freedoms and liberties, whereas the U.S. Government is looking more and more like they might be.
No offense, but it wasn't the US pushing for Chinese-sourced mass censorship of your internet...
See: Mao Zedong (Yale graduate) and Every US Ambassador to China is a member of Skull and Bones.
The best way to predict the future is to create it. :)
Citation needed, except that by definition there can't be one, because if there were such a public claim, and an un-shared piece of intel existed (that in theory would refute it), then that intel could not be used publicly to refute the claim. Since the claim is irrefutable, it is also invalid.
So it's probably more accurate to say 'extensive sharing...'