As far as the first point, make sure you know your statutes. Section 1 PACE, Common Law; once you learn it, make sure you know it verbatim. If you ever go to court over a use of force situation and you can't rattle out "I had an honestly held belief I faced a threat of imminent danger, so used force as I felt was reasonable and necessary to avert that danger" (that's not it word for word, but whatever) off by heart, then you're going to put yourself in a bad spot when they question you as to why you used force.

As for learning them, I'm a visual learner myself - so I made notes and used highlighters and just rewrote out the offenses and I know most of the big ones.

Discipline depends on the force's trainers, but /u/stopfightingthedog has a better answer than I do on that one.

For discounts, again, /u/stopfightingthedog has a better answer than I can provide, but you can sign up for the blue light card when you get your warrant card, and that's £5 for 5 years and it gives a wide variety of discounts both online and in store.

Don't worry about it, you'll do fine. Good luck!