Analogue broadcast TV services are now ceased in most EU countries and the Communications Ministries are relicensing their frequencies for use by “white space devices” for digital data transmissions. some of these frequencies were allocated for use by analogue wireless microphones.

So be careful that your current equipment, or any second hand equipment you might purchase operates on the correct new frequencies allocated to your country!

Otherwise, various bad things could happen. You could get in trouble from the enforcement staff of the Communications Ministry, or (more likely) some random device will suddenly appear on your microphone frequencies and create a loud hissssss / buzzzz noise on your audio (as it gets its allocation from a system which does not expect your mic to be there on that frequency) which will wreck your performance (and if you are unlucky, also your loudspeakers).

if you are unsure, check with your suppliers and/or Communications Ministry for your country (I have listed some below)

UK : Wireless Mics
NL : Agentschap Telecom – Verandering frequenties draadloze microfoons
DK : http://www.erhvervsstyrelsen.dk/traadloese_mikrofoner
DE : http://www.bundesnetzagentur.de/cln_1932/DE/Sachgebiete/Telekommunikation/RegulierungTelekommunikation/Frequenzordnung/FrequenzzuteilungAntraege/NoemL_NichtOeffMobilerLandfunk/DrahtloseMikrofoneBasepage.html