Roll the dough on a flour dusted surface to a rectangle about 25cm x 40cm. Spread the mustard over, then crumble over the bacon, cheddar and spring onions. Roll up from the long side like a swiss roll. Flour a sharp knife and cut into 9 slices. Lift onto a floured baking tray, spiral-side up, in a 3 x 3 square. Allow some room between the slices for growing.