By Karol Badohal Jan 13 (Reuters) - Poundland owner Pepco Group is betting on a fast expansion of its network of stores and tight cost control to boost its results, its chief executive told Reuters on Thursday after the company posted a jump in quarterly revenue. The owner of PEPCO and Dealz discount retailer brands, posted a 12% rise in its quarterly total revenue on a constant currency basis and like-for-like sales up 0.7%. At 1348 GMT the shares were down 3.8% at 42.58 zlotys ($10. If you ado...