What industry are you in? I only ask because you've listed Mines Rescue and from what I've seen over the last three years of 'transition' the extractives industry is really starting to get this training thing right.

Yes it helps that all our certified quarry managers have to have annual CPD (by law), but also organisations such as WorkSafe, MinEx, the IoQ, AQA and corporate sponsors have taken the lead and organised the days, so much of the training is not only free but also really, really well planned and enjoyable.

Now that the teams have been to a few training days they can see the real value in them. Our company also requires those who attend training sessions to briefly share what they learned to the team at the next toolbox meeting and reports are done for the board.

This lifts the level of conversation at all duty holder level. -> greater engagement -> less resistance to training -> etc

In my experience it is quite normal to close down for training sessions and I think it is great to be able to train the whole team together, work through any issues and have the team able to collaborate with each other. I think those few people who are negative maybe do not fully understand the importance of education.

When we or companies we work with shut down we send out emails to companies, post on our website and social media stating "We are closing for the day to educate ourselves. We want to make our company more experienced for you." This reflects the benefit to your customer. I also think that in the emails / website it is important (also a great conversation starter) to let the customer know what the training will be focused on if it is going to improve the quality of work. It will keep your customers feeling like they are included in the company and if they have been looking at doing something similar, encourage them to ask you questions to confirm if they should implement a similar training day.

Mostly this will come from a lack of leadership and poor culture. So like many organisations you have some work to do here!
Also look for informal leaders / champions who can help communicate positive messages about the day and h&s generally.

I have a family acquaintance (let's call them "Charlie") who likes to do things for other people. The things Charlie doees aren't what other people would actually want (and are actually sometimes against their express wishes) and usually impose extra work on other people to take part. Charlie then gets annoyed if everyone else isn't grateful for all the effort Charlie put in.

Even with the day described from your own point of view, you're taking away a day of operations to supply people with a set of information that you have decided that they need to have. It doesn't sound like you're being at all discriminating, trying to "cover off" everything, so for any given participant there's a good chance that a lot of the information will be irrelevant to their role, or a repeat of things they've heard before. You're "bringing in" people to do the training, so the quality, consistency, and cohesion of the presentations could be all over the place.

Now, I'm not saying that your day will actually be like this, but that's a typical experience people have of training days. That's what some of them will be primed to expect. The question you should ask is not "Why are they negative?" but "What am I doing to subvert their expectations?" They are entirely right to be skeptical, it's up to you to prove that they are wrong, so that they come up to you afterwards and say "Thanks, that's not at all what I expected. Good job."

A starting point might be to ask them about their experience of previous events, so you can make sure you don't repeat the things that have created their current attitude.

(I'm often one of the people "brought in" to speak at company safety days. The experience is highly variable. Some are planned months in advance by professional event planners who vet every presentation and ensure they blend into each other with a consistent yet interesting message. Others have mix of internal "death by powerpoint" and external "here's my generic talk I give at 200 workplaces a year" with bad AV and poor time co-ordination.)