Ofcom have issued its long-awaited updated 'Amateur Radio – Guidance for Licensees' document
The PDF document is intended to offer advice and clarification on the updated licence conditions.
Some Foundation and Intermediate holders had been under the mistaken impression they could not operate from a vessel in areas such as the Bristol Channel, the Solent, the Thames Estuary or the Wash.
The guidance provides further clarification on this matter and references a map, The Territorial Sea Limits of the United Kingdom, Isle of Man and the Channel Islands, which show the "Internal Waters" where Foundation and Intermediate Amateur Radio Licence holders can operate from a vessel.
In these water Foundation and Intermediate holders may either sign their home call sign or optionally add a /M suffix if they wish.
The Ofcom guidance can be download - http://licensing.ofcom.org.uk/radiocommunication-licences/amateur-radio/licensing-updates/guidance-oct2015/
Territorial Sea Limit Map - https://www.gov.uk/government/uploads/system/uploads/