Firstly, if you have any idea of what you'd like to do at Uni, I'd look at course requirements just to ensure that you're not limited by these choices. That being said, science subjects (including math) and English are considered 'facilitating subjects' so you should be fine as this should keep your options open.
Workload wise - should be okay. Since you have to take 4, art was probably a good choice since it's not *too* exam based as far as I'm concerned - meaning when it comes to your exams in the summer, theres no written one as such and all your art work should be done by that time, enabling you to focus on the other subjects. However, the problem with art being uni's don't take it very seriously for this reason, and tend to focus on the more academic subjects, unless you intend to go to some sort of art uni or something.
Good thing about 4 is that universities often only really take into consideration your best 3 results, although this could become an issue with art if it is one of your best grades, compared to the other subjects.
I don't have any experience with eng Lit at a-level, but from what I've heard it literally depends on the books etc that your school does as to whether you enjoy it so much. So, if your school does a significantly uninteresting book, you probably won't look forward to learning and revising it, and this withdrawal can significantly alter grades and that. That being said, at my school they seem to enjoy the books they're studying, especially the contextual parts.
Also don't do physics, but its very split with how people find it. Some get it, some don't. I would say though, doing maths does sort of compliment the physics side, and its often not recommended to take physics without maths.
I do Maths and Further maths so that's something I can help with aha. Not gonna lie, it is pretty difficult. Concepts can take time to get around (maybe because we're doing the course in one year?), so an emphasis is definitely put on practice. I quite like the math homeworks though, a good break from any essay based subjects (I do politics and geography too). No reason why anybody cannot do well with the practice. Completely different to GCSE though which a lot of people don't understand. Very proof based compared to the problem solving at GCSE, and a lot of trigonometry too and graphical stuff. None of that nice construction stuff or anything aha. Just have a look at what you're in for BEFORE you take it. Mechanics is fairly similar to what those who do physics do, so that would definitely compliment your learning in that respect.
Again with Art, very heavy on workload despite the lack of written exams. It can be time consuming to do preparation etc, similarly to GCSE I guess. But if that's your thing, and you're able to keep up with that and enjoy the art work despite also having other subjects to do work for then you should be fine.