Stapleford is not in Kent of course; and the D.O.C. of an air to ground frequency is usually limited to a maximum of 10 miles from the station. This means that pilots should not be trying to transmit on the frequency outside this range. By doing so they may be causing all sorts of problems for other units that have been also been allocated the frequency (in different geographical areas) perhaps amongst them Brest Control!
Suspect that some of the instances posted here are based on transmissions outside the D.O.C.s of the airfileds concerned. Also it is entirely possible that the ground equipment at some A/G FISO units is not subject to the same regular testing of performance and levels that ATC units would be, and therefore may be transmitting at a stronger signal than they were licensed for.