The Brooks B17 is one of my favorite saddles and it works just fine for me when riding with an upright bar cockpit.

At least two issues could be contributing to the lack of comfort. Saddle needs to be broken and/or your butt needs the same thing - to toughen up. I go through this each year, between riding seasons. My Motobe is long gone, now, but was a wonderfully comfortable bike to tool around on...