I did one of these 1day courses when I was 20, didn't know anyone in aviation and had absolutely no idea about what the role of cabin crew is and what it entailed.
I would say that there a lot of crew and ex crew on here who could give you all the information you need rather than spend a lot of money on a course. I have done a bit of cabin crew recruitment in the UK and was crew for a few years, so if you need any more info, I can help you out.