I had the same question the other night, check out this thread:
http://www.subsim.com/radioroom/show...182964&page=97
My first post was one post back, bottom of page 96. Never did find U-459 at the first or second location, but that part of the mission was considered complete for me. I than used the normal "request resupply" feature of the radio man to
actually get fuel from a tender out there.