Commuters struggling to get to work on an unreliable train service and worried about high interest rates hiking up their mortgage bills were on Wednesday branded “grumpy” by a minister as he sought to persuade people to vote Tory.Science minister Andrew Griffith adopted the seemingly unusual approach of trying to woo voters, including many in London and the wider South East “Blue Wall” commuter belt, as his party flatlines in the polls on around 20 per cent, more than 20 points behind Labour.