For me buying already made biscuits are easy because all you have to do is blend them. To get the ingredient in this recipe to work well, and taste great, you need to add a dry biscuit crumb mix. My only other alternative idea to make this recipe taste nice is for you to make your own batch of biscuits from a basic biscuit recipe, using your preference of flour (i.e. gluten free, wholemeal or wheat meal).
Once these are baked and cooled I would blend them and continue on with the recipe.
I have seen people use flour or blended oatmeal instead of blended biscuits/cookies and the results have tasted quite bad. Although if you find a nice tasting alternative the let me know!