Frederick E Moysey, son of Commander Frederick Abel Moysey was not the Captain of the Belliver cargo ship when it sank.

Captain of the Belliver when it sank in 1911 was Frank Ernest Moysey born Plymouth 1871.
His parents are John Moysey and Sarah nee Lamble. They married Sept 1/4 1847 registration district Kingsbridge Devon.
John died 20 January 1893 and Sarah died 1895.

The children of John and Sarah Moysey are
John Moysey born 1847
William Moysey born 1850
Samuel Moysey born 1852 died 1852
Samuel Moysey 1853
Philip Henry 1855
Sarah Mary Elizabeth Moysey born 1856 died 1922 never married
Alfred Henry Moysey born 1859 died 1863
Ellen Moysey born 1863
William Henry Samuel Moysey born 1865
Charles Moysey born 1865
Charles Herbert Moysey 1869
Frank Ernest Moysey 1871 died 1911

Frank Ernest Moysey was indentured as an apprentice in the Merchant Navy in London 6 November 1888 for 4 years.

Frank Ernest Moysey, Captain of the Belliver, married Florence Parker in 1896. They had 6 children
Ellen Moysey born 1895 died 1904
Ernest Frederick Moysey born 1899 married Gladys M Gregory, one child Anita G Moysey born June 1/4 1923.
Gertrude Ellen Moysey 1900 married Hutchinson. No children.
William John Moysey born 1903 died 1911
John Moysey born 1906 died 1911
George Moysey born 1907 died 1907

So of the two children who did not die with their parents Ernest Frederick is the only one who had a child, Anita and she emigrated to America. Her obituary gives the names of 4 children.

Looking for any Moyseys in the UK you would be looking for the descendants of Frank Ernest's brothers and sisters.
Christina