Travis Perkins, Britain's biggest supplier of building materials, warned of a challenging 2023 as housebuilders slow down projects and home-owners delay improvements due to the country's gloomy economic outlook.    Travis Perkins, which sells bricks, timber and new kitchens, as well as equipment for large construction projects, said adjusted operating profit fell 16% last year to 295 million pounds ($355 million), behind a consensus forecast of 320 million pounds.    The miss was blamed on restructuring costs from closing 20 smaller branches out of the group's 1,500, which Chief ...