Thanks for the responses!
I have finally managed to get in touch with the shop I bought it from, and apparently when the owner gets back into the country in a week, he might order more, and I might get a replacement through him. All in all it's been a very frustrating experience especially considering how much it cost and I wish I just hadn't bought it..
My normal pattern of use has been to leave it charging all night and all day without using it at all. Then I get home from work and watch one half hour TV show, using it intermittently while leaving it plugged in. Before the TV show is finished, having used maybe one third/one half of the loaded material, the batteries will be completely drained and the lights will flash red/blue to indicate overheating.
If I do the same thing, but unplugging it while I use it, it runs out of batteries much faster, and when I plug it in after it runs out, it flashes red/blue anyway. So then I blow on it to cool it down until it will charge, and leave it plugged in for an hour or two, after which it will be at maybe 20-50% charged, and I can get another 5-10 minutes use. Repeat until I go to sleep. Extremely conservative use (making sure when it is at vape temp I get the most use possible out of it, et c.) and aggressive charging tactics (blowing on it to cool it down enough to charge whenever possible, et c.) means I can get through maybe 1 1/2 loads in a whole night if I am lucky, careful and diligent.
At first I thought this was just the best experience possible, and was on the verge of giving up on vaping all together (as this was meant to be one of the best vaporisers around), but after reading about it I'm pretty sure it shouldn't be acting this way.