Ben and Holly is made with CelAction. As are many other animation series: of note to mention here is Peppa Pig.
Developers of CelAction2D, the most powerful 2D animation software in the world
www.celaction.com
A similar animation style could be done with Moho Pro, OpenToonz, or Toonboom Harmony (Advanced or up edition).
In theory Adobe Animate CC could also be used, but since CS6 it went downhill and is now too buggy and performance degraded to such an extent that even with the help of the great Flanimate plugin it isn't considered to be a good idea.