Thanks for your comments Laszlo. They've helped me. I have created a multi-build script, and I have created all my Ant projects as subprojects of this, although I still have to put the source code into them and fix the dependencies.
Perhaps it isn't really a concern, but I've noticed that NetBeans creates Gradle build scripts in Groovy. Is there any switch to instruct NetBeans to create them in Kotlin Script? Might there be an easy way to translate Groovy to Kotlin Script? Thanks again, Owen.