William the Conqueror (aka William the Bastard) of Normandy invaded in 1066 and supplanted King Harold, the last of the Anglo-Saxon kings. William's was the last successful invasion of England by a foreign power.
There was an unsuccessful invasion of Wales (but not England) by the French in 1797. The invaders looted food and wine and after two days, too drunk to fight, they surrendered to a local militia led by Lord Cawdor. According to local rumour, they mistook a large group of Welsh women onlookers for "several thousand" British redcoat soldiers and so were disinclined to offer any resistance.
During World War II German forces occupied the Channel Islands (from 1940-45), but these are not part of the UK. You can find photographs from this period showing British policemen alongside German soldiers.
Scotland isn't being invaded.
At various times in its history, Scotland has been invaded by the Irish, Vikings, Romans, English.
Norway as a sovereign country has never invaded Ireland. But the Vikings of Scandinavia invaded England, Scotland and Ireland for hundreds of years.
Scotland
Scotland
Scotland
Scotland
Scotland
Scotland
Scotland.
It could be Scotland.
Presumably Ireland or Scotland.