Is the UK going to invade..........

The Diplomatic and Consular Premises Act 1987 would work in this case.

It wouldn't work in this case Otto.
The provisions in that Act only cover change of status by the Secretary of State if it is done in compliance with the relevant international law and treaties, which puts it back under the vienna conventions which means it can only do it with Equadors approval.

Britain really screwed up with its threatening letter.
What on earth were they thinking