Tickets on cross-Channel ferries will rise in price by £50 because of new EU emissions rules, operator P&O Cruises has announced. P&O, Britain’s biggest operator, said a return ticket for a family of four traveling from Dover to Calais will increase in price from £160 to £210 from January 1. The company blamed new rules set in Brussels, which force operators of ships in the English Channel, North Sea and Baltic Sea to adopt more expensive low-sulfur fuel, called marine gas-oil. They will also have to install filtering equipment, called “scrubbers”, costing millions of pounds. …