Mix together the flours, baking powder, salt and the 75 g (3 oz) sunflower seeds in a bowl. Stir in the yogurt and mix to a fairly soft dough.
Shape the dough into a log on a floured surface, then drop into a greased 1.25 kg (2½ lb) or 1.5 litre (2½ pint) loaf tin. Brush with a little milk and sprinkle with the remaining sunflower seeds.
Bake in a preheated oven, 220°C (425°F), Gas Mark 7, for 20 minutes. Reduce the oven temperature to 160°C (325°F), Gas Mark 3, and bake for a further 30 minutes. The base of the bread should sound hollow when tapped. If necessary, return to the oven for a little longer. Transfer to a wire rack to cool. Serve with cheese or Smoked Salmon Spread, if liked (see below).