I think it depends what you are considering doing at uni, and if you think you will actually finish it (we were told only 1/3 of people who apply actually finish it!) If you're thinking of applying for competitive unis/courses it's very good to show you have a wider interest in the subject and are actually committed to studying it further! I think it depends also on how many alevels/extra curricular things you are already doing - think about if for you it's worth it.
I found it very fun and interesting as it allowed to me explore a topic I hadn't in college, and I really enjoyed it!