Block UK access now just in case.
It'd be interesting to see how fast the policy would get reversed then.
This was always a stupid policy and so protesting it by pulling services is one way to draw attention to that.
Microsoft + Google + Amazon + Nvidia + Meta + Apple = $630 billion in annual operating income.
They'll react to a change in capital investment faster than anything else.
Damage to stock value would be the bigger blocker (from both sides of the pond).
Might kickstart some actual competition though, as that happening would create a large hole to fill.