Received a promotional email from Next - I don't have an account with them but I do subscribe to emails.
You will receive one £5 Next gift card when you spend £30 or more in one transaction on products from the School Shop between 15th-18th August 2019. Gift cards can be redeemed in UK stores only and not online. Offer limited to one gift card per customer.
Possibly store specific - definitely in Leeds (Trinity & White Rose) but I can't find a list of participating stores, they're not in the T&Cs