In thinking about my question above, I'm safer sticking with the original 315mA, as here in the UK the voltage is around anywhere from 230V to up to around 250V, so the 500mA is 59% higher rating than the 315mA, i.e too high for our voltage, so the 20% to around the 25% margin really only applies to 115V. So here in the UK we are probably better sticking to the original fuse rating.