Preheat the oven to 180ºC/gas 4 and line a baking tray with greaseproof paper.
Lightly dust a work surface with flour and divide the pastry into two evenly sized pieces. Roll one piece of the pastry out to roughly the size of an A4 sheet of paper (no thicker than 2mm), with the longer side nearest to you.
Spread the green basil pesto evenly over the pastry, leaving a 1cm border at the top, and lay 8 of the pancetta slices vertically on the pastry.
Scatter over half the grated Parmesan and roll the pastry up into a tight spiral cylinder, starting with the longer edge closest to you.
Brush the top edge with a little milk to seal and, using a sharp knife, slice the cylinder into 1cm thick pinwheels.
Arrange the pinwheels on your lined baking tray, flatten each one slightly with your hand and pop in the fridge to chill while you prepare the remaining pinwheels.
Repeat the above steps with the second sheet of pastry but use the red sun-dried tomato pesto in place of green.
Bake both batches of pinwheels for about 15 minutes, until crisp and golden. Serve warm.