I have found with mine, Its attached to the visor, and if I have the visor flipped up, with the device between the windscreen and the visor, I have not had to change the frequency.. When I arrive at work (In crawley) I turn of the device and the frequency I am using has a clear station on it, but the Jabra over powers that signal... Its that good!!
It does not auto seek, but one press of a button on the Jabra increments the frequency by .1 so its very easy to flip it, not that I have had to, but I have not driven In London with it.
Buy it, try it, Hate it send it back get a refund!