A suggestion I've seen for using Roundup on English ivy is to do it in the spring when the leaves are young and before they've developed their waxy repellent coating. I agree with Daisy, I'd be surprised if vinegar killed more than the tops. It usually only works with very young tender weeds (herbicidal vinegar is also stronger than supermarket vinegar). On more established ones it tends to kill the leaves but not the roots (I don't think most ordinary liquid dish soap would be considered organic BTW).
Might you have a picture of the problem you could share with us?
