I have to say that I have never heard of cosmolight. I have obviously heard of Ianro QuartzColour who were part of the strand group until recently. It appears the cosmo people bought QuartzColor in 2012 so it is the original company and hopefully the build quality is still as good as in the past.
Like I said before I have a cheap chinese redhead that I got for free (actually I think it was supposed to be the other way around and the lighting gel was free but I was after the lighting gel) the difference between the QuartzColor red heads (I have a set of 3) and the nasty chinese one is simply night and day. The QuartzColor lights are very usable and nice as far as redheads go. The chinese one is a dodgy piece of rubbish in poor condition. Not moaning, it will probably come in handy somewhere but if I was choosing between the two it wouldn't be much of a choice.