If a British citizen or member of the British Armed Forces dies overseas, a death certificate is issued by the relevant authorities in the country concerned. Additionally, the death can often be registered at the request of the deceased family, by the British Consul or High Commission in the country where it happened.
The death certificate will need to be taken to the Registrar of the district in which the burial or cremation will take place. The Registrar will then issue a Certificate of no liability to register. This will then be given to the funeral director to allow the funeral to proceed.
The following external link goes to the General Register Office's webpage on registering an overseas death, with details of useful addresses, including the Overseas Section of the Foreign and Commonwealth Office
www.gro.gov.uk/gro/content/deaths/registeringanoverseasdeath/