If you have met all the AP requirements by that particular department at UCL, ( I have taken 6 APs by the end of my
junior year) , is it almost guaranteed that you will get an offer? What other area can go wrong besides writing a lousy personal statement? Thanks!
Nothing in life is guaranteed except death and taxes. I assume you have read the UCL website, they are pretty specific about entry requirements so if you have the correct scores in relevant subject, along with a solid personal statement you should be good for an offer. I would caution that you heed the cost of studying in London, if you are on a budget give yourself plenty of wiggle room. Good luck!
In general, if you are paying international fees, meet the requirements, have a solid (more than not-lousy!) PS, and a decent LoR you are most likely to get an offer for most courses at UCL (not medicine; a few other very competitive courses may be fussier). The tighter the fit of your APs to their program the better.
What having all the AP requirements in hand does mean, is that if you get an offer it would be unconditional.