I have got my Restricted Radio Telephone Operators Certificate – now called an MROC I believe (maritime Restricted Operators Certificate). But we will also need to get a call sign for the yacht, and some countries require a ships radio licence as well, although Coastguard say on their website that:

In most cases a standard GURL (General Users Radio Licence) or ships call sign is all that is required for vessels travelling overseas. In some cases when engaged in international voyaging a vessel owner may have difficulty in convincing a foreign port authority that the Radiocommunications Regulations (General User Radio Licence for Maritime purposes) Notice 2007 and a callsign record in SMART constitutes a valid radio licence, hence vessel owners may choose to maintain an individual licence for their vessel (and pay an annual fee) so that they can present a copy of the radio licence to officials in foreign ports. To obtain an application form, contact Coastguard Boating Education (info@info@boatingeducation.org.nz).
A Maritime Ship (radio) Licence consists of a licence number, a call sign number, an MMSI number and depending on the vessel type, a radio telex number. The Maritime Ship Licence is an individual radio licence granted to the owner of the vessel.

• New Zealand call signs can only be issued to New Zealand vessels. If the vessel is registered overseas then you must contact the licensing authority of that country to obtain a callsign.
• To operate a MF/HF (SSB) radio, a Maritime Restricted Operator Certificate (MROC) is the minimum requirement.
• The cost is $350.00 per year.

So I guess this all leads back to the decision as to where to register the yacht…

It seems that new VHF radios also have the capability of transmitting a digital code – MMSI – Maritime Mobile Service Identity – this can be obtained when you apply for your VHF call sign for an additional $10.00. The call sign cost is $45.00.

You also need to register your EPIRB on beacons.org.nz

If the yacht is registered in the UK then the licences are free if you register online at http://www.ofcom.org.uk. You need to register your VHF, EPIRB, AIS, Personal Locator Beacons and Radar too.