I did most of the training to do my IAM test, then moved to somewhere there wasn't a local group, so never went any further.
I'd absolutely take issue with the "smug complacent bellends" comment - that wasn't remotely the impression I got from those running the training. They were serious - sometimes to the point of earnestness
- but if anything, the advanced training was about
reducing complacency and smugness. I guess there wasn't much about being a bellend, at least not specifically.
And I still use a lot of the stuff I learned 25 years ago in my driving now, and am absolutely certain that it has improved my driving and ability to be courteous and safe on the road as a result.