I've emailed Samsung asking for a replacement battery but got this as a response:
Thank you for your email Michael, we recommend to return this back to the store it was purchased from so the battery can be sent into an authorised service centre to be assessed.
Being a known issue I do think the stores should stock replacement batteries for Galaxy devices just like mine. I've got a problem though, when I got my S4 sent away for repair they requested the proof of purchase (fair enough) but they've never returned this to me. Now I'm having to go through the whole grabbing my proof of purchase all over again. I know they've got policies to adhere to but I do think a problem like this (especially in my case where the back of my phone no-longer fits on) should warrant Samsung to go "Right, we've got a problem, let's just set up a site, grab the serials and send out batteries to the affected customers"
My Galaxy has actually only been in my hands without problems for less than a month, I don't know if I've had bad luck or what, but I've had faulty Gorilla Glass when I first purchased it, and now it doesn't hold a charge at all.
So my question is, is anyone on this forum experiencing the same issues with their batteries? You can find out if you've got a potentially faulty battery by just seeing if it's made in China (faulty) or Korea (new).