Are USB sockets on wall outlets live all the time, even when the switch is off?
In the US, no the USB ports will not have power when the outlet is not powered. Most outlets in the US don't have power switches on them, so if you switch them off there is no way for power to be provided.


In the UK, outlets often have power switches. In that case, your USB ports are usually powered while the outlet switches are off. This is because the outlet assembly itself is always powered, but the switches only control the outlet and not the USB power transformer. 

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You said cheers in your original post, so I'm assuming you're probably British and have the UK type of USB outlet. Yes, this is normal.

Other answers are assuming that you are in the US, where that wouldn't be normal.