Hallmark Cards Inc. agreed to buy British rival Creative Publishing for $306 million in cash in a deal that would create Britain's biggest greeting card group with nearly 30% of the market. Executives at Hallmark and Creative Publishing said they anticipated no regulatory problems with the merger, because there is little overlap in their businesses and the British greeting card industry will remain highly competitive. They also said no layoffs are planned. Hallmark is a leader at the high end of Britain's greeting card business, selling fancy cards at premium prices. Creative Publishing makes cards sold in boxes, such as Christmas cards, for much cheaper prices per card. Hallmark Cards, the world's largest manufacturer of greeting cards, is privately held and based in Kansas City, Mo.