Yeah I have exactly the same problem. There is a phone number to call if the voucher doesn't work has anyone tried it yet? I haven't done it yet as I imagine the switchboard wlll be busy . If I do get through I will let you all know what they say.
Good luck!!
Update: Just got through (surprisingly quickly) and the customer service chappie informed that me that the emails have been sent through with incorrect codes and they are working to rectify it ASAP. He told me that the updated emails with the correct codes should be sent out within the next couple of hours but I won't hold my breath!!