DH10OFF
Found this while being bored and browsing at Cashrewards. Not really sure about the one time use? Also, dont forget 8% cashreward cashback to get a total of 18%. Not as good as the student promo but still better than nothing. Enjoy.
"10% OFF all orders, for both new and returning customers. Voucher is only valid for online payment, and can only be used once per household."
It wouldn't be a total of 18% discount unless cash rewards are giving 8% cash back on the original amount. If the 8% off the discounted amount is applied then overall % will be less.