Found this guy when looking for cheap solar panels and how to power stuff off grid when the power goes down (rare here, but when it happens food gets too warm in our fridge). I was also sick of the UK energy companies raiding my pay packet just to power a fridge and telly. So if you're into that these sorts of videos are worth a look imo.
I think these are iron based as its safer. The nickel ones are safe but dont last as long and have to be treated right.