First up take whatever you are using to detect the issue and move it towards a large metal, but non-electrical object, to test that it's not your receiver that's faulty or wiring just working as an antenna! If you are using an energy saver "mains conditioning" plug, then remove it - this is a possible future conversation...
I'd suspect that if you placed whatever receiver it is that you are using near any outlet on the same ring main - even with nothing plugged in - you will get the hum. Test it to see if that's the case! If it is, see if the hum disappears if you turn off the circuit breaker. If that cures it, then you'll need to unplug *not just turn off* everything on that ring main to see if the issue remains with the breaker both on and off. If the issue remains with the breaker off, then you have an issue external to the ring main, or possibly in the consumer unit itself. To cure that situation you'll probably need a qualified electrician! Alternatively, if the hum had disappeared, then you should be able to go around testing what happens as you plug devices back in one by one!
Good luck, and keep us updated.
