That's enough to make the UK ~40% immigrant in one lifetime (80 years). Given how rare it is for countries to change so significantly so fast, it's fair to say that they already have very liberal immigration. The UK population rose from 63 million in 2011, to 68 million in 2023, despite a below-replacement fertility rate of 1.74 [1].
While it's true that most nations in Europe want lower immigration [2,3,4], such sentiments rarely translate into policy, similar to the US.
[1] https://en.wikipedia.org/wiki/United_Kingdom
[2] Europeans overwhelmingly against immigration: Poll (2011) - https://www.euractiv.com/section/social-europe-jobs/news/eur...
[3] Europeans Most Negative Toward Immigration (2015) - https://news.gallup.com/poll/186209/europeans-negative-towar...
[4] Poll reveals great unease among Europeans about migration policy (2022) - https://www.brusselsreport.eu/2022/02/01/poll-reveals-great-...