One of the perks of being a student (despite all the costliness of being one) is student discount; it's pretty much everywhere you go. So if you're a student, or even in sixth form you can get this. You can confirm your student status here.
Or if you're like me and your Sixth Form wasn't on the list, you can use ID in store, or an NUS card. But all universities are.
Right now there are loads of places you can get an increased discount so here are some of the things I would go for...
Motel Rocks always has 20% off for students but they've bumped it up to 25%
Check out the full list here