Rub the inside of the fondue pot with cut clove of garlic. Pour in wine and lemon juice and heat gently until bubbling. Reduce the heat to low, add curry paste and gradually stir in grated cheeses, then continue to heat until cheeses melt, stirring frequently. In a small bowl, blend cornflour smoothly with sherry, then stir into cheese mixture and continue to cook for 2-3 minutes until mixture is thick and smooth, stirring frequently. Do not allow fondue to boil. Serve with pieces of Nan bread.