You start paying back your student loan as soon as you graduate
There really isn't much to add to this section as the rules are very simple:
You won't be expected to pay back a penny of your loan until the April following your graduation, at the earliest. Therefore, if you graduated in June 2018, your first payment wouldn't have been taken until April 2019 at the earliest.
This means your first year of post-uni life is payment-free, and even then you'll only start repaying if you land yourself a graduate job and are earning above the £26,525 threshold.
For some who never earn above this threshold, it may mean that you never pay a penny back but we will explore repayment costs in the next chapter.