I am close to someone who did. Took time but was worth it. Also, having gone through the process, the police took more notice with subsequent calls were made when told that they knew about relevant criminal history of the partner/ex partner.
Sorry, forgot to add they called 101 and said they had heard about Claire's Law and wanted to check a partners/ex partners history and they took it from there. They were put in touch with a specially trained DV policeperson