Looks like you are up a creek without a paddle, on the visa application it says you must declare every conviction. When you fly out you will have to answer weather you have had any convictions on the entry card, if you answer yes they will question you regarding it then they may find out you filled in your application falsely, then they could cancel your visa. Or if you say no then you are making a falce statement again, both are grounds to revoke your visa.
Personally I think you should have been honest from the off and then you would not have been in this situation.