Audrey, as long as the weight matches, you can use any flour pretty much.
There's a shop at Malaga Markets called Uncle Franks. You buy all your grains, seeds etc by the scoop. Buckwheat is really cheap there. I get all my spices and everything from them. Awesome stuff there.
Hope you went ok with your bread! I made bread tonight too. I wanted an extra practice before my first demo tomorrow night.