Some Help Please!

I have a 1997 Audi A4 and i'm unable to get into the car due to the locks not working. We don't have a remote to it, we've always used keys. I'm able to get into the boot but neither the passenger door or drivers door will let me in.

Could it be that the battery is flat? Can i get through somewhere in the boot? Is there some manual override trick i can do?

thanks