If they genuinely offered underhand deals to a British person then they'd be well minded to do a little more than simply refuse, we have some of the strictest laws in the world on paid promotion and advertisement, you can't do that kind of stuff(Taking payments, free stuff, ect, even stuff like heavy airbrushing is illegal in UK advertising) in any UK video content, reviews or not, without very clearly stating it before hand, if there's implication MSI are enticing British citizens into breaking these laws then ASA would have a huge case on their hands. I ofc don't believe for one second OC3D would be implicated in that though.
Good Tom Scott vid quickly covering UK paid promotion laws and the historical reasons as to why Britains are so strict:
https://www.youtube.com/watch?v=4SyetdjWMuw