Business is booming in the most profitable town in Britain, despite the average business seeing a fall in profits, a survey revealed yesterday. While the overall national average profit margin for small and medium-sized enterprises fell from 3 per cent in 2000 to 2.8 per cent in 2001, those in Bexleyheath, south-east London, increased profit margins from 13.5 per cent to 15.8 per cent. It was the second year running the town had topped the annual survey by business analyst Experian.