My father's now cancelled his purchase of the Sunderland tickets. After being told we could have a full refund on the membership but still pay the price with the £10 discount as a goodwill gesture for the mistake, we've now had a call from the ticket office manager saying we can only have a part-refund and even then we have to pay the difference to pay full price for the tickets, with no discount.
A very disappointing experience, if I'm honest. I thought Saints would handle it far better than that.
Hero to zero whoever went back on that decision.