One thing you can try is refrigerate the wine to see if any of the tartaric acid will precipitate out, this could take 2-3 weeks. You could also add sweetener to the glass to try and strike a balance of acid and sugar.
Actually the best thing you can do i think is to add Calcium carbonate (CaCO3). Take 2 or 3 bottles, and add different ammounts of CaCO3 to each bottle. Its very hard to doit after you have already bottled the wine, but start adding 1/8 of a teaspoon or less to a bottle. You can buy this in any chemestry shop. Make sure de CaCO3 is food grade.