Well I still can't find Jacks' father's Birth registration! Given as 12 Dec 1909 on his Death Registration below.
England & Wales, Civil Registration Death Index, 1916-2007
Name: Christopher Carey
Death Age: 68
Birth Date: 12 Dec 1909
Registration Date: Apr 1978
[May 1978]
[Jun 1978]
Registration Quarter: Apr-May-Jun
Registration district: Plymouth
Inferred County: Devon
Volume: 21
Page: 1782
Christopher Carey was the eldest of 12 children born in either Limerick or Cork according to the family history.

Marriage 27 June 1942 at RC Church Douglas, Co. Cork
Christopher Carey Full Age, Bachelor, Naval Rating of Balliureskig or Ballinreshig.
Father John Carey, Labourer
Spouse: Mary Anne Lynch, Full age, Spinster Full Age, Housekeeper of Douglas W.
Father John Lynch, Labourer. Witts:. John Carey & Eva? Lynch