Please don't take this as absolute gospel as I have not read the official documents and am not an expert in the technology. However I understand, from a knowledgeable person at work, that the EU have some new regulations affecting 2.4 GHz radio systems that came into force on 1st January this year.
Equipment that complies with the new requirements is not compatible with equipment to the old standard. Effectively if you go out and buy a new receiver, it may not work with your old transmitter and vice versa. There is nothing to stop you using the old equipment, but the EU will not allow the import of any more equipment to the old standard after the start of this year.
Apparently suppliers have been aware of this situation for some time but did not expect it to apply to relatively low power model radio systems. Unfortunately the bureaucrats decided differently. Some manufacturers are coming up with fixes to modify old equipment to the new standard but it will still not be possible, for example, to have a receiver that will work with both. The fix might be embodied by an owner applied software update or might need equipment to be returned to the supplier for modification.
As a further effect I also understand that Spectrum DSM 2 equipment cannot be modified to meet the new requirements and will therefore no longer be imported into the EU.
How this will all pan out I have no idea but the scope for buying incompatible gear seems to have been significantly increased. If any one has any more detailed knowledge of the situation, let us know. If you are thinking of spending money on a new system in the near future, do your homework before parting with your cash.
Gareth