Hi,
Not sure if this is relevant, but I remember, years ago, driving up the M6 through Cumbria towards Scotland whilst listening to Radio4 198KHz long wave from Droitwich. The further north we went the more noticeable a peculiar "phasing" effect became. We were receiving the same programme from Droitwich and another LW transmitter in Scotland, but don't know which one. At that time FM reception was very poor in that area, so we gave up and switched the car radio off.
Cheers, Pete