I DID e mail the GRO with the following question and received the following answer:
I would like to order the birth record of my 5th great grandmother born in Kent in 1831. While most parish baptisms do not carry the maiden name of the mother, would her birth record have the maiden name of her mother since she was registered under the GRO Regimental Birth Indexes? What info would British Armed Forces And Overseas Births And Baptisms show from 1831?
In case you need it the person in question is:
data entered with GRo Registrationnumber...
So prior to ordering would this record list her mother's maiden name?
The following answer came today:
Thank you for your enquiry.
The records we hold at General Register Office relate to births, marriages and deaths which have been registered in England and Wales since 1st July 1837. For more information visit: GOV.UK
The main source for records of life events before 1837, such as baptisms, marriages and burials, are parish registers and records of other faiths see National Archives
To continue researching prior to 1837, you may wish to consult a professional genealogist or genealogical records agent. For more details see Society of Genealogists.
Good luck with your research.
Should I take from this that the GRO regimental births prior to 1837(mine is 1831) are not actually kept at this office?