Greetings welcome to the Forums.
Use of an herbicide might have been a good choice here, though they are more effective if there are leaves on a plant when the herbicide is applied. At this point I would complete your repairs and just continue to remove all visible leaves and stems that you see. This will weaken and kill the Ivy (Hedera helix, I presume) as it won't be able to photosynthesize. The ivy stems growing in darkness under the wall, were only extensions of the growing plant outside in the light. They will not grow in darkness for long without an external source of nutrition.