(Reuters) - A.G. Barr Plc forecast higher full-year revenue on Friday as more people bought its fizzy drinks, but flagged continued economic uncertainty in Britain and regulatory intervention in the soft drinks industry. The maker of Irn-Bru, Scotland's "second national drink", said it expects revenue of about 277 million pounds for the 52 weeks ended Jan. 26, 5 percent higher than a year earlier.