Saw this at my local shell where we have a family account. the guy behind the till gave me loads of vouchers but the code is the same for all. valid until 15th March 2017 and can be used for a month to access all magazines.
Edit: if you are being asked to provide card details try using another email address which has not been registered before
Edit 2: if using mobile use link belowhttps://gb.readly.com/shell