I've been to 4 or 5 of these over the last ten years or so, and from that position I'm going to be slightly controversial. I think that these safety evenings have lost their way slightly.
The main objective now seems to be to frighten GA pilots into not going beyond their limits - all well and good. But doing so with lots of "though shalt nots" instead of constructive advice about the best way to fly safely isn't in my opinion all that helpful. Also some of the advice being given, particularly with regard to microlights, is just plain wrong (the fatal accident rate being quoted was about double that in CAP701, and the explanation of the tumble - a current hot-topic in microlight circles, seriously contradicted the published work on the subject from places like "Microlight Flying" and "Journal of Aerospace Engineering".
For the time being, if you've time and inclination to improve your safety understanding my recommendation would be to use the events organised by GASCo or the PFA (or some commercial ventures such as that run by Irv Lee) which have better researched better qualified speakers (and GASCo is now run by John Thorpe, who used to do the CAA safety evenings). You don't get a stamp in your logbook, but for my money you'll learn far more of real use in keeping you safe.
As to the accident record of safety evening attendees - whenever I've been to them the audience are all the more experienced and cautious pilots anyway; the people who need a bit of education rarely go. That I think is the main reason for that statistic.
That said, it does no harm to be reminded of rules and best practice, and it's a good opportunity to pick up some of CAA's (excellent) safety literature, so not a complete waste of an evening. But, far less useful than it should be.
G
Genghis the controversial.