Frustrated business owners say they are suffering a slump in trade after Southern Water closed off part of a busy High Street. Sewer repair works in Herne Bay started last Tuesday and have already had a drastic impact on footfall in the town centre. Chyna Ma, who runs the CM Beauty Academy and adjoining coffee lounge, says she is missing out on about £300 to £400 a week in revenue because of the closure, with the waterworks right outside her door. “I am driving into work in a bad mood because I know the cafe is going to be absolutely dead, when it would normally be busy,” she said. “It’s havin…