Not sure how things work on the other side of the pond, but in the US it's illegal and against FCC regulations for an end user to change the crystal in any transmitter.

*Transmitter Crystals Can Not be changed to another channel except
by a licensed service center. It is against FCC regulations, and
illegal for the user to change a frequency determining component
of a transmitter. If the radio is not retuned, it can be a hazard
spectators, modelers or property, and void AMA insurance coverage.