|Kit of parts|
I seems that everything it working and that I haven't managed to damage the components with the excess heat.
The MOSFET on it gets pretty warm. As in I can just about touch it briefly, but it doesn't melt skin warm. I think this is normal. My multimeter is unable to read the voltage whilst the dusulphator is connected. I'm guessing the, in effect, AC voltage is too much for it.
I'll keep an eye on it to make sure it is not overheating, but you need to run them for several weeks for them to work apparently.