1) To make the dough, combine the water, yeast, and honey and let sit for 5 minutes or until the mixture is foamy. Add the flour and the salt and mix until well combined and a dough is formed. If the dough is too sticky, add a little more flour.
2) Turn out onto a lightly floured surface and knead until the dough is smooth, about 5 minutes. Place in an oiled bowl, cover, and let rise until doubled in a warm, draught-free spot, about 45 minutes to 1 hour.
3) Preheat oven to 190C/Gas 5. Knead dough together with 4 tablespoons of oil, 60g sugar and a pinch of salt. Roll half of it out thinly into a rectangular shape the same size as the baking tin. Grease the tin and line it with the thinly rolled out dough. Sprinkle with 4 tablespoons of sugar and half of the grapes. Roll out the remaining dough and put on top to form a second layer. Sprinkle with the rest of the grapes. Let in rise in a warm place, then sprinkle with remaining sugar and cook for 30 minutes or until well risen and golden brown.