Why won't my cream biscuits rise?
The recipe is fine; if you follow it carefully it should work. Things you might mess up:


Baking powder isn't baking soda; make sure you have baking powder.
If you leave the dough alone for hours before baking, the baking powder will expend itself.
It's silly, but make sure you used a tablespoon of baking powder, not a teaspoon.


Working the dough longer won't help - if anything it'll make the biscuits tougher. And double cream is a bit more fat than heavy cream (see this question), but it shouldn't be a big deal.