Given the average level of Power-supply-design expertise of Arduino forum readers ("nil"), I find the suggestion that they might be able to use some random cheap LED-driver module from eBay as a power supply to be ... dangerous. That's probably the reason that tempers in this thread are running a bit hot.
Don't misunderstand, I'm not trying to insult you but, BULL! Go back and look at the very first page and the first few posts. With the exception of Lefty, all the posts are insulting and sarcastic. But, I've gotten used to that over the years; it seems there is always a race to be the most deprecating first. If one is really worried about the newbie getting in over their head and blowing something up or getting shoved across the room by mains voltage, just say so. Something like, "This is messing with mains power and can really hurt you, and here's why it may be a bad idea" would probably do the trick.
And you folk that do this kind of thing know full well who you are.
Like I said, I keep coming back here because there are a large number of really helpful folk that actually respond.....eventually.