By Mark PiesingFeatures correspondentGriffon HoverworkHovercraft were a quick way to zip across the world's waterways but were noisy and expensive to operate. Could they be about to enjoy a second wind?The 12.30pm midweek hovercraft departure from Portsmouth is already respectably half-full when we step on board. Marketed as the world's only year-round scheduled passenger hovercraft service, the Union Jack-emblazoned machine flies for a thrilling 10 minutes, hovering just inches above the water’...