By Guy Taylor A new rail service between London and Stirling has been given the green light by the regulator and is expected to lower fares on the West Coast Mainline. The Office of Rail and Road (ORR) said it had given the go-ahead to Grand Union trains, an open access operator, to start the service between the capital and central Scotland. Grand Union trains will introduce four new return services per day from London Euston and Stirling stations. The new route will call at Milton Keynes Central, Nuneaton, Crewe, Preston, Carlisle, Lockerbie, Motherwell, Whifflet, Greenfaulds and Larbert. It …