I think I have had a breakthrough!
I have been liaising with Herefordshire Registry Office and they have the following information:
Charles Davies
06/08/1880 DAVIS CHARLES JOHN LABOURER PREECE MARY ROSS 25/149 ROSS 305523
This is just a year out from the year of birth that Charles gave on the 1939 Electoral Register
However, there is a query on the mother being called Mary as there was no marriage of a John Davies and a Mary Preece but there was this marriage
John Davis Marriage Date 3 Nov 1876 Marriage Place Ross, Hereford, England
Father John Davis Spouse Eliza Preece Father William Preece
There is also the following census information relating to John & Eliza
1881 census address Kyrle Street, Ross, Herefordshire
John Davies Head Married 38 1843 General Laborer Ross, Herefordshire, England
Eliza Davies Wife Married 27 1854 Ross, Herefordshire, England
Charlie Davies Son Single 8 months 1881 Ross, Herefordshire, England
1891 census address Morley Square New Street Ross Herefordshire
John Davis Head Married 40 1851 Sexton Herefordshire, England
Eliza Davis Wife Married 36 1855 - Wales
Charles Davis Son 11 1880 Ross Herefordshire, England
Harry Davis Son 3 1888 Ross Herefordshire
1901 census address 34, Kyrle Street, Ross, Ross Urban, Herefordshire
John Davies Head Married 50 1851 Grave Digger Ross, Herefordshire, England
Eliza Davies Wife Married 46 1855 Ross, Herefordshire, England
1911 census address 29 Edde Cross Street Ross, Ross Urban, Herefordshire
John Davis Head Married 40 years 5 children 3 still living 70 1841 Ross Herefordsh
Eliza Davis Wife 60 1851 Ross Herefordshire
1901 census address Bryn Clwyd, Clocaenog, Ruthin, Denbighshire, Wales
Edward Davies Head Married 48 1853 Farmer Bala, Merionethshire, Wales
Sarah Davies Wife Married 46 1855 Llanelidan, Denbighshire, Wales
Charles Davies Servant Single 21 1880 Teamster On Farm Ross, Herefordshire, England
1911 census address Pen Y Par K Bryn South Marchog Near Coawen, Clocaenog, Denbighshire, Wales
Charles Davis Servant Single Wagoner On Farm 30 1881 Herefordshire
I will order the birth certificate to confirm that Charles's mother is Eliza and not Mary and hopefully this will confirm whether all the above assumptions are correct.
Thank you all for your help so far.