That`s correct Alan, it`s an offence to use a VHF unless anyone on board is qualified (and unless the vessel is registered/licensed), however you can licence the boat in advance of being qualified.
The course is approx £70 for the day plus i think £20 for the registration on completion.
so long as at least ONE person on board is qualified then it`s legal for anyone (under supervision of the qualified person) on board to use the VHF radio.
EVERYONE who owns a boat should complete the course , not for legal reasons but just for safety ....