growstuff
The total number of immigrants to the UK is much higher than the population of Norwich. I assume you're also concerned about them.
Migrants who come here to either study or with a job to go to, have to provide documentation and evidence that they can either support themselves if studying or that the job they are coming to has a salary of over a certain level.
They contribute to society on day one, they do not have unlimited free access to healthcare, free housing, free food etc. in fact I think they have to pay an amount upfront in order to access NHS services.
The unfortunate people crossing the channel who risk drowning arrive with zero documentation, are taken care of by the state (and rightly so) have immediate access to all healthcare care services, cannot work legally. (According to the BBC documentary many work illegally for food delivery firms).
No comparison, for the security of the U.K. in these increasingly difficult and somewhat dangerous times it is imperative that we know who is entering this country, where they are from and why.