If you're worried about the fruit sinking to the bottom of the cake, add a few scoops of the plain batter to the cake pan before mixing the berries with the rest. Once the cakes have cooled ...
When making dense fruit cakes such as a Christmas cake, the batter needs to be heavy enough for the dried fruit and nuts to be suspended in it; if it's too thin the fruit will sink to the bottom.
Add the dried fruit and orange zest. Bring to the boil, then remove from the heat. Leave to cool a little, then beat in the eggs and fold in the dry ingredients. Scrape into the prepared cake tin ...