British oil rig builder Lamprell sees full-year revenue slipping to the bottom of its guidance range because of stagnant oil sector investment and losses at a windfarm project, it said on Wednesday, sending its shares sharply lower. The company said that total losses on its East Anglia One (EA1) offshore windfarm project would be about $80 million because of mounting costs for unplanned staffing and equipment requirements. "We anticipated a challenging 2017 given the weakness of our end markets…