Hey,
I'm really sorry you're going through this. What I would suggest is get a job immediately so you can save up as much as you can, if, worst case scenario, your parents cut you off. Does the college/sixth form you go to offer some paid jobs for sixth formers to do at school? For e.g. mentoring younger students, community service etc. My school does and the hourly rates we are paid here are better than some normal jobs so do look into that for your own school! If not, look for a weekend job that doesn't require you to stay out too long (from what I can tell, your parents probably wouldn't be too pleased to see you coming home late at night from work).
Perhaps you've already tried this but really try to
talk to them as well -- sit them down one day and attempt a civil discussion one more time. If you know they'd never listen then it wouldn't do you harm to lie a little bit. Give them fake statistics, like how 45% of students in London unis graduate with practically worthless degrees and 50% of top graduates across the country come from unis that are outside of London [it would be helpful if you mentioned some of the unis you applied to as the most "successful" unis]. Tell them that women are more in danger of being in London unis then they are in Unis outside of London etc. Make up some fake articles and come home from school one day, and tell them some recent news about the increase of crime around London unis. Normally I'd say it's kind of terrible to lie to your parents, but if they really want to hold you back from achieving your dreams and being happy, then maybe they're not very deserving of the truth. When your parents, or ANYONE, is getting in the way of your happiness then you've got to take a stand, otherwise you'll end up trying to please people for the rest of your life and being miserable, and constantly thinking of "What ifs".
To avoid the risk of being physically harmed/stopped by your parents, ask one of your friends in advance if it'd be okay for you to stay over at theirs in case there is an emergency. Leave a bag of clothes/other necessities at theirs so if anything goes bad, you can run over to theirs. Put them on your emergency contacts on your phone so you can call them quickly if your parents start threatening violence, so they can come over to get you. Obviously I really hope it never has to come down to this, as ultimately I'm sure your parents' over protectiveness comes out of love and concern for you. If they really have your best interests at heart, they will, even reluctantly, allow you to go to your desired university. Also, don't tell them you have applied to out-of-London universities until AFTER you are sure they would be okay with it. And when you do tell them, make it seem as though you've recently applied, as if you did it after you got their "permission". Controlling parents like to hear that they are the main and only influence of decisions, so that might even please them.
All the best to you and remember that your dreams are very, very important. Let nothing, not even the fear of losing your parents, limit you from reaching your highest potential. Life is too short to let people who supposedly love you stop you from enjoying it! Good luck!
<3