Whisk together the flours, xanthan gum and salt and set aside.
Add the sugar to the milk and stir to dissolve. Add the yeast, stir and set aside for about 5 minutes until foamy on top.
Whisk the eggs and egg yolks lightly in a mixing bowl. Pour in the oil slowly, whisking constantly.
Add the yeast mixture, all at once and the vinegar and whisk to mix.
Add the flour mixture, all at once and beat well for 4 minutes.
Add the orange zest, raisins and sultanas and mix to combine.
Cover the bowl with a damp tea towel and leave to rise for about 1 hour until doubled in size.
For the glaze
Whisk together all the ingredients.
Heat the oven to 190°C (170° fan) 375°F gas 5.
Line a baking tray with non-stick baking paper.
Scoop the dough out onto a heavily cornflour dusted surface and dust the dough with cornflour, adding more as needed. Knead and punch down the dough until smooth and no longer sticking to your hands or the surface.
Divide the dough into 3 pieces.
Roll each piece into a 30cm|12" long rope (roll between your hands from the middle, working outward).
Pinch the top portions together; braid into a plait and pinch the ends together, sealing the ends together well.
Form into a circle and pinch the circle closed.
Place on the baking tray and leave to rise for a few minutes until puffy.
Brush the top of the braid with the glaze.
Bake for 30-40 minutes, until golden brown.
Sprinkle with sugar nibs whilst warm. Place on a wire rack to cool completely.
To decorate, place the coloured eggs in the centre of the wreath.