It is true that migration is what has made us the people and the great nation that we are. Slow, steady assimilation of small numbers over hundreds of years.
But it's different now. The rate of population growth in recent years is massive, look:
Population 1997 (Blair) 58.3 million; 2020 (23 years after Blair) 67 million. Increase 8.7 million or 15%
Population 1974 (23 years before Blair) 56.2 million; 1997 58.3 million. Increase 2.1 million or 4%
The rate of growth of population started increasing in 1979 (Thatcher became PM later in the year), it continued to increase until 2011 (Cameron), since then the rate of growth has been dropping.
Scource- 2nd graph
U.K. Population 1950-2024
Chart and table of U.K. population from 1950 to 2024. United Nations projections are also included through the year 2100.
www.macrotrends.net