What is the best course to do for a rookie in computer science?

I'd like to get into cyber security or the tech industry but haven't studied computer science...

Most Computer Science degrees don’t expect an A Level in Computer Science, but they do expect excellent Maths. See UCL Computer Science degree as an example but of course there are many other options.

This organisation, STEMettes, supports women into STEM subjects. I would recommend going to some meet ups and events and sign up for the newsletter so you can find out more about your chosen path.