There's another post somewhere where i rant probably, but to be short, I have heard of a few auto extinguishers and not heard of any bad ones. They come in many different designs.
Amongst a lot of other work, i fit and commission "Fireboy Xintex" suppression systems on luxury and super yachts.
They are definitely the nuts, based in Poole. FM200 gas fills the area in a split second, removing oxygen and cooling.
Vehicle engine compartment extinguishers is where they started out. Not sure of its the same gas but it will be quality.
They still supply for vehicles as I'm promised a kit at mates rates any time now.