Two goals from Siriki Dembele helped steer Grimsby to a 3-2 victory over mid-table rivals Cheltenham.The pacy winger proved too hot to handle for the Robins' defence and it took him just 15 minutes to open his tally, finding the bottom right-hand corner from a Paul Dixon cross.Cheltenham rallied and were back on level terms in the 26th minute when Mohamed Eisa's cross picked out Harry Pell who guided his header beyond visiting keeper James McKeown.But two goals in three minutes just before the break wrapped up the points for the Mariners.In the 42nd minute the home defence failed to clear a corner and central defender Danny Collins forced the ball over the line.The Robins were still coming to terms with that when a delightful chip from Sam Jones picked out the unmarked Dembele who calmly placed his shot past keeper Scott Flinders.Cheltenham pressed for a way back into the game in the second half but failed to break through the solid Grimsby defence until Carl Winchester netted five minutes from the end.Nigel Atangana shaved the upright with a header in added on time but Grimsby held on for the points.