>>13209656Yeah, I did this at a UK uni.
I started off with Physics+Math, dropped the Math after the first year, and just took a random humanities module each semester (sometimes two, dropping the one I got the lowest essay score on). I had a great time. I did History, Philosophy, and Film Studies. Basically, as long as you do the core component modules for your degree, you're all good.
I would say though, that you have to be careful. Picking up a random physics module is likely to fuck with your score if you haven't done the prerequisites. Also, since the courses all tend to stick together, you might find it a bit cliquey doing other modules sometimes. STEM modules is probably easier in this regard, since half of them are Chinese or autistic anyway.
As for joint honours, I'm not sure that's possible outsidenof very specific combinations. UK degrees are generally less flexible, so you get 75% of one subject as core modules, with only enough space to cram in 25% of another (Electronics Engineering with CS, for example).