British tycoon SIR Richard Branson's son SAM's 21st birthday plans have been thrown into chaos following the terror alerts across Britain yesterday (10AUG06). The music student invited 25 pals to join him on his father's Caribbean island Necker to celebrate his big birthday, but found his flight plans in chaos upon arrival at London's Heathrow Airport. At least 24 people have been arrested and thousands of Britons' holiday plans have been disrupted or cancelled as the country is put on a critical level of alert after the alleged discovery of a plot to blow up US-bound flights from the UK.