Paul Murton visits the islands of Coll and Tiree, which though just a few miles apart could not be more different. On Coll, he meets Nicolas Maclean Bristol, owner of Breachacha Castle, who can trace his ancestors on the island back to the 14th century. Tiree is one of the stormiest places in Europe, but is also one of the best places in Britain to surf and practise the relatively new sport of sand yachting, the racing of go-carts with a sail along the beach.