By Kate Holton and Sachin Ravikumar LONDON (Reuters) -Britain recorded its hottest day ever on Tuesday, with the temperature exceeding 40C (104F) as a heatwave gripping Europe intensified, forcing train tracks to buckle and fuelling a spate of fires across London. The Met Office said a new provisional record temperature of 40.3C (104.5F) was recorded in Coningsby, in central England, with 34 sites across the country experiencing temperatures in excess of the previous high of 38.7C (101.7F) recorded in 2019. Stephen Belcher at the Met Office said he had not expected to see such temperatures in …