Prestwick has also been asked by the MOD to delay the switch over for certain frequencies.
The transmitted frequencies of the ground stations have not change one iota, its only the dials on the equipment that have changed. The transmitters all have the same bandwidth, its only the receivers that have had to be narrowed to accomodate the in between frequencies. The MOD equipment would still work perfectly well with those who have adopted the new designators, so asking them to delay is pointless.
The driving force behind the move is the spectrum tax imposed by Offcomm on the ground stations. Its 1/3 the price for an 8.33 channel.