Ollie, you should have, by law, a license for either fixed or handhelf marine VHF. It can be obtained from the Radiocommunications Agency, Wyndham House, 189 Marsh Wall, London, E14 9SX. Tel: 020 7211 0215/0217 or e-mail AMS@ra.gsi.gov.uk
It cost me £20 for 12 months and you do require a callsign when you complete the application. My license came through in a week complete with a windscreen holder similar to a car road fund license holder.
Hope this helps.
P.S. If you get into trouble and haven't got a license, USE the radio.