Were I a British citizen, my answer would be an unequivocal YES!
Britain should not waste time deciding whether or not stay in the EU!
To stay is to surrender more of your own sovereignty.
In these mad days, it is wiser and safer to have full control of your country's immigration policy instead of trying to be politically correct when that would mean endangering your own safety for the sake of some silly concept.
In time, who knows, you might not even have any sovereignty left worth talking about.
Besides, the EU is the sick man of Europe now!
Your London mayor is right. If the small dot that is Singapore could make it when it was unceremoniously kicked out of Bolehland, why couldn't you?
If you couldn't, that tells the world that you are useless!