I notice MetOffice have issued weather warning for Thursday in the South: http://www.metoffice.gov.uk/weather/uk/uk_forecast_warnings.html?day=3
Heavy rain is expected to spread north-eastwards during Thursday across parts of southern England and South Wales, with torrential downpours and thunderstorms possible in places.
The public should be aware of large amounts of spray on roads and, in some places, minor flooding.