Given I can't just pop out and buy a pack, and cassava flour, the main ingredient is available in my local Asda I thought I'd try and teach myself how to make them from scratch.
I used this recipe. The results tasted right, but they weren't nearly as light and round as the mix buns, and looked more the shape of rock cakes. Lots of googling around indicates that this isn't uncommon, but I want to make the more rubbery dough that can be shaped with your hands into balls, and then those balls frozen.
I used the butter option, but next time I'm going to try it with sunflower oil, add the flour directly to the hot liquid in the sauce pan and mix in the pan until it's combined as you would do with a choux pastry and see how that works. If it's still a little soft, I'm going to have a go using an icecream scoop to put it onto the baking sheet.
Even so, despite their visual imperfections these still tasted fantastic. Seriously. Even if you're not gluten free give these little babies a go.