Wireless Mics and In-Ear Monitors in the UK are generally available at VHF (170 – 210 MHz) and UHF (470 – 865 MHz).
There are 3 ways you can legally use them:
The ranges 173 – 175 MHz and 863 – 865 MHz can be used without a licence subject to the requirements of The Wireless Telegraphy (Exemption) (Amendment) Regulations
These ranges are also used by other low power equipment so can be subject to interference.
VHF and UHF Shared frequencies can be used anywhere in the UK once licensed. The licence can also cover anyone hiring from the licencee.
Co-ordinated frequencies are licensed at a specific site for short or long term. They provide the best protection against interference.