Hi there, I currently study International Relations (which falls under Politics) and Arabic at university, and can hopefully offer some useful insight!
I had never studied Politics before starting my degree, but this didn’t cause any issues for me. Many UK universities are aware that some students will begin without a subject-specific background, so the first year is designed to get everyone up to speed with introductory modules that cover the basics. My university also offers additional support through academic writing workshops, but since you're taking History (which is similarly essay-based), I think you'll adapt quickly.
I did take French at A-Level, though, and absolutely loved it. You get to study a wider range of topics, such as literature, film, current affairs, and contemporary issues, and can reach an intermediate language level, which is great for diplomacy. You'll also get to do an independent research project on an area that interests you—I did mine on French secularism (which actually tied into politics!), but others explored topics like fashion or healthcare.
If I had to choose, I'd lean towards French—it gives you a tangible skill that you can use long-term, whether while traveling or for work. But honestly, you can't go wrong with either!
I hope this helps, and good luck with your decision!