Those A Levels sounds fine together to me!
Although to do a Law degree you don't necessarily need to do Law A Level (or so I've heard) it might be worth doing it at A Level if you can, more to see if you actually enjoy than anything.
Don't worry about having to 'compete with the new students.' Majority of universities don't really mind if you've repeated a year, unless it's like, Oxbridge or something. I'm currently at Liverpool University and I repeated Year 12 for various reasons (did Biology, Maths, combined English) and non of the universities I applied to seemed to be fussed about it.
So long as you've got something to put on your personal statement when it comes to applying to uni, I don't see why it would make such a big difference!