Let’s make it worse key scenario aka if you’re not a British citizen or have visa sponsorship like extra EU then you’re not able to legally reside, work and get healthcare in the UK. What do you think the government will do? Deport 3 million citizens (lets make 2 if a million leaves beforehand) back to their countries breaking families and households?(I guess the cost of doing this would be much higher than what was promised to go to the NHS). Force British people who are now on benefits to work the minimum wage to make up for the gap left by EU citizens? Strike a deal with India and replace EU migration with Commonwealth? I do not see any of this happening, and there is even still the option of a soft Brexit which would allow the UK to still be in the single market. In case of hard Brexit there will be a deal, especially for London and for EU citizens who resided and pay tax in the UK. What we can do now is build the best professional profile that we can, so if this country will go down, we will definitely not drown with it.