Don't know what "for ie" means, but basically, it's not asylum seekers getting smuggled in who are the big problem. This might be the study that I had read, reported elsewhere:
"Unauthorized immigrants are non-EU-EFTA citizens who entered the UK without permission and have an unlikely path to permanent residency. The population also includes those who may have entered lawfully but overstayed a visa. Asylum seekers waiting for a final decision in their case are included in the unauthorized immigrant population estimates. Their future status is uncertain as rejection rates are high."
https://www.pewresearch.org/global/f...nited-kingdom/