If a death occurs at home, then you will need to contact your GP or an ambulance. If the death was expected, then the attending doctor will provide a medical certificate stating the cause of death - this will need to be submitted to the Registrar of Births, Deaths and Marriages. If the circumstances are unexpected or the doctor is unsure, then the death must be reported to the coroner and the deceased will need to be taken to hospital for a post-mortem.
If death occurs at a hospital, the hospital staff will obtain a Removal Order from the family and then transfer the deceased to the mortuary. If required, the hospital will request to carry out a post-mortem. Ensure that you collect any personal effects from the hospital, and ask the hospital staff about the medical certificate.
If the death occurs abroad, it must be registered according to the laws of the country in which the death occurred. The death must also be registered in the UK via the British Consulate of that country.
A death should be registered with the Registrar of Births, Deaths and Marriages within 5 days - this should be done at the nearest registry office.