You only have 1 personal statement. That means you will (in general) need to apply for one subject. It will be very hard to convince a law admissions tutor that you are dedicated to studying law when half of your personal statement is on computer science. I think the logical route forward is for you to find out which of the courses you want to pursue, as you won't be able to submit your application for a while now. Its absolutely fine not to know what you want to do at this time in year 12, but if you want to apply to university then you will have had to have made a decision. Of course, some combined honours courses might work out for you, or you might be one of those people (a la Viola Helen) who successfully apply for a variety of similar courses, but the vast majority of people apply to 5 of the same course at 5 different universities.