Here in the US we have the National Restaurant Association that offers Servsafe courses, both in person and online. While I am sure that you have something different in the UK, I would assume that there is some form of national program that offers courses and certification that a Google search should find.
Once you find your program equivalent to ServSafe you should see if they offer a handbook and invest in that. Begin with taking each day and going over a new chapter. Quiz yourself and take online tests related to the program and practice as much as you can. It is quite important to learn how to do things the right way. It's a lot to learn but it's foundational and quite necessary. The only way I think to prep for the tests is to take the time to study and practice tests. If you work in the industry ask those of your peers if they are certified and maybe they can help you.