How do I get onto a computer science course with no experience?

I think it would be wise to contact universities directly, but unfortunately in your case it seems like the best case scenario would be to register to sit 1 year A levels for summer 2018, choose more relevant subjects to study this year. Typically CS require Maths and sometimes Physics so you should check degree requirements at universities you are interested in applying in. One good option might be applying to courses with a Foundation Year (I don't know much about these but from what I understand they are aimed for people with limited experience with A Level Physics and Maths who are interested in vocational degrees like Engineering, Computer Science, and STEM subjects.

I think it is absolutely worth pursuing Computer Science if you know it is something you are truly interested in, but you will have to probably i) take A level courses or ii) Apply for Foundation Courses. But definitely contact the unis to check for certain- I'm sure that'll clear things up a lot more!

I will be in Tanzania teaching English during 2018 exam season Maybe I will try foundation, thank you

I'm on a gap year and got A*, A, B in Law, Psychology and English Language at A level and B in Sociology at AS. Obviously these are NOTHING to do with computer science and every other forum I've read people have been like "I've have no experience and have A levels in maths, physics and chemistry" like obviously they're going to get on :/ . I've got loads of experience from my gap year stuff that would get me onto a good business course but it's really not my passion so do I sacrifice going to an alright uni for something I'd hate and go to a horrific uni? Will I even get into a horrific one for computer science with my grades/experience??