Rich people like their privacy, especially on holiday. And those who cater to their needs learn to keep their mouths shut. Which made Sir Richard Branson’s Caribbean holiday retreat an unpromising subject for a documentary. Billionaire’s Paradise: Inside Necker Island  (6 January) was notable for its dearth of billionaires, unless you count Richard Branson himself. He lives and works on Necker, assisted by “two lovely ladies” to whom he dictates his emails. But the 74-acre island is also available for hire, at £280,000 a week, or, if you are not quite in that league, you can take a room at £30,000 a week. We met a few of those comparatively thrifty guests. Kerry and Pat were a Brummie couple. Pat works as a part-time bicycle mechanic. Kerry has the