(Corrects period in seventh paragraph to 2023, not 2022) (Reuters) -Homebuilder Bellway on Tuesday warned of operational challenges and slowing demand as mortgage rates climb, leading to flat volumes next year as the housing sector also comes under pressure from a broader cost-of-living crisis. UK housebuilders benefited from strong house prices and tax breaks during the COVID-19 pandemic but have had to contend with a surge in building costs while homebuyers’ purchasing power is squeezed further by rising interest rates as central banks seek to tame inflation. Britain in September cut stamp d…