I've only tried welchs wine once when I was in my infancy of home brewing. Brewed it right in the juice bottle with a balloon on top. If memory serves me correct I used bread yeast. It was bad. I still have nightmare over the taste. I may have to try to redeem myself and try it again......with the correct ingredients.
if you used bread yeast and didnt add any sugar im sure it tasted horrible...I have made some and it actually didnt turn out too bad. If you are looking for fine wine go to the liquor store or start growing grapes....you won't get it with concentrate and you shouldnt expect too.