There have been studies to show that immigrants put more into the economy than they take out , so immigrants are a financial benefit to the UK
Our findings show that immigrants to the UK who arrived since 2000, and for whom we observe their entire migration history, have made consistently positive fiscal contributions regardless of their area of origin. Between 2001 and 2011 recent immigrants from the A10 countries contributed to the fiscal system about 12% more than they took out, with a net fiscal contribution of about £5 billion. At the same time the net fiscal contributions of recent European immigrants from the rest of the EU totalled £15bn, with fiscal payments about 64% higher than transfers received. Immigrants from outside the EU countries made a net fiscal contribution of about £5.2 billion, thus paying into the system about 3% more than they took out. In contrast, over the same period, natives made an overall negative fiscal contribution of £616.5 billion. The net fiscal balance of overall immigration to the UK between 2001 and 2011 amounts therefore to a positive net contribution of about £25 billion, over a period over which the UK has run an overall budget deficit.
https://www.ucl.ac.uk/economics/about-department/fiscal-effects-immigration-uk