oh nigel 10 A / mm2 ? thats not at all pessimistic, thats better than the chart you linked to, I've always worked by the rule of 5A/mm2 but then I like to make sure there will be no problems, considering its a heater and therefore the wire may find itself in an already "warm" working environment I think it should be thicker, I think 8.3 amps needs more than 0.75 mm2, the other issue being that the fuse is rated at 13 A so the cable should capable of 13 A no point in a 13A fuse if there cable is going to catch fire before it blows. of course it depends on the wires temperature rating, but then dare I assume that in china they used anything better than the worsed ? (in the case of your chat 60 deg which can carry 6A)