As ORAC says, this information has been in the public domain for months now and planned behind the scenes for quite some time prior.
Think about it: with inherently in-built interoperability, why WOULDN'T you test and operate USMC F-35B with UK ones, on the world's only purpose-built F-35B aircraft carriers?! This is called increasing capability for mutual benefit folks... Sure, it's a way of plussing up the firepower on our decks early on, but the Marines are keen, so again, why not?
I suspect the OP is attempting to incite outrage from what is, ostensibly, a logical move.