Radios can suffer from interference from other radios on the same frequency. The PMR446 license-
free channels are available to the general public, so can be interrupted by other users.
An Ofcom license costs just £75 for 3 years, giving you professional channels to use, but these are not exclusive, so can still potentially suffer interference from other racers.
You have to press a button to transmit, which can be a distraction for junior drivers.