Britain invaded?
Of course not! The last time that happened was during WW2 when jersey and guernsey were occupied by german forces.
Recently jersey saw some hostile ships nearing their coasts. It turned out to be yellow jacketed french fishermen loudly protesting their outrage at the UK breaking the trade and cooperation agreement (TCA).
Some french politician, eager to be elected come next french elections, threatened to cut of electrical power to jersey. Stupid of course, and not necessary. The TCA provides for quick punitive measures in case of the UK going back on their word. Slap on tariffs and the british do a u-turn. Their pm is the world beating driver of u-turns.
So if the EU slaps tariffs on all fish the british export to the EU, they'll soon find their place.