Genealogy / Looking for ancestor's grave in a cementery in Warsaw [9]

Hi, I am off to Warsaw tomorrow and this is my last chance to try and get the information i need (I have been trying for months). I have one photograph of my Grandparents grave and I would love with all my heart to visit them. I have no information as to where it is but I am guessing Warsaw as this is where my Dad was born. Can anyone tell me the best place to go to try and find out what cemetery they are in. I leave late on Monday so if there is a registry office in Warsaw that I can go to and ask, this would be great as all internet searches come back with nothing. I hope someone can provide me with something. Thank you