I'm pretty sure that you're arguing in bad faith here. It's not exactly subtle nuance to distinguish between well-integrated, contributing immigrants versus asylum seekers and low-skilled immigrants who will be net takers all their life.
The UK is still very welcoming to the former group. No one has suggested zero migration. Most of us have colleagues and friends who are immigrants - often family too - and are very happy they are here.
Why are you pretending you can't tell the difference? Don't you see that it's you who is being racist with that?
So to make your suggestion a bit more realistic, let's divide all immigrants into those 2 groups - the ones we want and the ones we don't - and only have the second group go on strike. But at the sane time, they can't use state services either No using the NHS. Their kids not in schools (but we can keep the same total school funding for the lower number of students, since the overall tax-take isn’t noticeably lower) so teachers don't need to deal with high numbers of kids with EAL. £4billion annually which was spent on the illegal immigrants available for other things, plus whatever we're spending on their Welfare. Twice as much social housing available in London. Sure, fewer carers. I have several family members who found care work satisfying but too poorly paid - without low-cost immigrants to tap into, perhaps that would change. Fewer men loitering on corners, barber shops and vape shops.
Really not sounding so bad.
You know that we set the immigrantion criteria, right? We can be much,much pickier about who we accept - setting the bar for highly skilled migrants to genuinely be highly skilled, not care workers and artists; and restricting student visa applications to serious subjects and post-grads at respected universities, not dodgy little language schools which don't actually expect their students to turn up to class; and having language tests and cultural integration mandatory for citizenship, as other countries do.
We just need the political will.