If you are looking at Open University you will need to do a
Bachelor of Science Degree. Specificity comes from attending a university.
From there you can do Postgrad courses although you need to confirm this. Most Uni's have good support to direct you.
In your case I looked at Job opportunities on the Open Uni website and that mentioned the best approach, but you may want to contact them to confirm.
I am studying Physics and Engineering but to get a specific outcome I can only go to a University (Curtin university). I have been lucky to be involved in the Student Army project for the Murchison Widefield Array (MWA) working for the University and as a First Year that is difficult to attain that kind of internship.