My 5.1 Logitech Speakers recieve radio stations in different languages sometimes it is french, english, polish, arabic, german. It usually happens on evenings. I don't live near any radio station also my neighbours don't listen radios in those languages. It is quite funny because even when I mute my speakers i can still hear the radio. To stop radio playing i can only swich speakers off.
Those speakers are quite brand new it did not happen before, i also did some research on the google and some people said to split cables because when they are all together they might generate a anthena and they just pick up the radios up and play it. So i did it and still radio is playing, changing itself volume and so on so ever.
How in the world can radio frequencies all the way from Germany reach you? If you live in America I would find that very hard to believe. Military signals COULD reach you with appropriate hardware and the right encryption code, but civilian transmission? It would take a really strong antenna several hundred feet in the air to get low frequency signals across the Alantic.
EDIT: Oh you said England. Much more reasonable. But still it does raise questions on to how a copper wire in a speaker system create a strong enough antenna to get the signals in the first place.
I had this problem not too long ago. I relocated my amp and speakers and have not had the problem since. Mine were located near a metal duct that I think was picking up the signal. I didn't try it but Ferrite core filters are also supposed to help prevent EMI/RFI and you can get snap on filters to put on existing cables.
AM radio travels quite far at night. It has to do with differences in the ionosphere between day and night. I used to be able to pick up AM radio stations around 1000 miles away at night, never could during the day but late at night it came in clear. I've also read that people in New Zealand can pick up stations from Australia at night.