My bread book is very insistent that unbleached plain flour (not bread, just plain old plain flour) is used. I wasn't sure whether my wonderful el cheapo Aldi floor was unbleached, so I bought some organic flour from the health food shop. Twice the price for half as much and the results today have been, quite frankly, disappointing. I've made two loaves that even though they were baked in a tin, look more like ciabatta (still taste great though) and have had a disastrous attempt at pitta breads.
I'm going back to Aldi tomorrow, especially as I've since found out that all UK sold flour is unbleached