I did it immediately after passing my test, decades ago. No longer a member, but only you can decide if its worth it.
Go for an assessment drive and see what feedback you get.
The whole purpose of it is about defensive driving, which some think means driving like Miss Daisy. It doesn't, it means thinking about your driving and taking advantage of situations to make progess.
It also teaches you to avoid getting into situations which may result in an insurance claim!