I was wrong.
When I actually did the test, I was stunned to see how an ingredient as simple as flour in bread and butter in a biscuit can make all the difference in the end dish.
I still want to buy value for money ingredients, but there are now a few items I don't compromise on anymore: butter (I don't ever use margarine), olive oil, jam, etc and of course chocolate.
Chocolate is, of all ingredients, one that must be of good quality, or whatever you bake (or cook) with it will just taste average, at best.
My favourite brands so far are Nestlé dessert (which I import from France), Meunier (available at least at Sainsbury's), and for top quality: Valrhona.
Speaking of chocolate, here is a selection of my favourite recipes so far:
My "Best Of" Chocolate Recipes
(click on the title to view the recipe)