First it was loyalty cards, then it was voucher codes. The UK market is one of the largest in terms of loyalty card users, and Boots’ Advantage card was one of the forerunners of this, rewarding customers with points for every purchase that they made. This was quickly followed by voucher codes, with companies sending strategic email deals to offer substantial discounts on flowers close to Mother’s Day and money off mulled wine at Christmas. Groupon is one of the leading websites that offers targeted voucher codes to....