Not sure what that means. What do you think the Uk claims to own?
Lots of european countries owned colonies until the post-war settlement.
And immigration to UK is at an all time high so not sure on other point?
Immigration to the UK is not at an all time high - both immigration and net migration are down pretty sharply:
https://www.bbc.co.uk/news/articles/c70989jrdweo
Immigration to the UK is not at an all time high - both immigration and net migration are down pretty sharply:
https://www.bbc.co.uk/news/articles/c70989jrdweo