He says: "One was on the phone, one was just walking around the shop, and the other one asked for £100 Ukash voucher. I said 'Give me the cash first'. He offered a credit card, but I said 'Cash only'. I was suspicious because of the amount and because they came in together."
They left and that was the end of it. It certainly supports Ukash's advice in the last issue: "Always take the cash before producing the Ukash voucher."