In 2066, GB won't exist.
There'll just be one gigantic urban sprawl called Londonopolis with distinct areas like "Little Manchester", "Little Pakistan", "Little Cymru", etc.
There'll be a stand-off at the Londonopolis/Scotland border with bulldozers trying to expand North being thwarted by Scots terrorists nicking all their diesel to power the lightshow at the Alex Salmond Memorial Theme Park.
I could be wrong.
Perhaps "Little Pakistan" should read "Greater Pakistan"......
As a point of order..
Will the USA exist in it's current form in 2066?
Will California and other southern States join a greater Latin America Federation leaving a depleted USA to try merging with Canada?
Interesting times.