There is a growing website called MyUNiDAYS that will offer you a discount code for online stores so that you can get student discount without an NUS card.
The website is fairly new so there aren't many stores partnered with it yet, but it should grow after some time, they are currently having talks with more companies to allow them to offer the service.
The stores that you can get discount for so far are:
- Fashion Union
- La Senza
- Occasional ASOS discounts
All you have to do to start getting student discount is sign up for free! You will be asked what university you attend and then you will need to use your university log-in to verify your account.
I am so glad I have found this website as I haven't been able to get round to buying an NUS card yet haha.
I hope this was helpful for you!