I am a history enthusiast, so I am probably biased here. But, History is a very good subject, and I think it will provide a good balance to your STEM subjects- it will show you are academically well rounded. It is also a facilitating, or 'traditional subject' as the Russell Group refers to them, and so it will be seen in a better light than Philosophy, but probably on par with French, and maybe Economics (though the Russell Group's Informed Choices leaflet does not include Economics as facilitating).
I hope I helped, but remember, I have cause to be biased. Lmao.