Bear, we are talking of hundreds of thousands of Jews who immigrated from 1920 thru 1945. According to official British records 367,845 Jews immigrated during that period legally and probably another 50-60,000 illegally (according to British law).
If they had not immigrated, most of them would have been dead (R’L) by 1945. If immigration had been kept fully open during this time then hundreds of thousands more Jews could have been saved.