Sharks, palm trees, shipwrecks and sandy shores are all vital ingredients for a sub-tropical paradise. Add sunken treasure, colourful corals, nectar sipping birds and exotic flowers and it sounds a long way from Britain. But the exotic Isles of Scilly are just beyond Land's End. Here Britain's biggest predator, the grey Atlantic seal, basks on the rocks and raucous colonies of nocturnal birds fill the midnight air.