Prison service instructions say Staff must not ask to see a GRC but can request sight of a birth certificate. Where an offender does offer a GRC as form of evidence and identity, they must be treated in the gender identified on the certificate. (from here, scroll down to download the word doc - 17/2016 The Care and Management of Transgender Offenders. Para 4.1)
The government guidance for GRC applicants has this to say:
7.3 New Birth, Marriage and Civil Partnership Certificates
• If your birth has a UK birth entry on receipt of a full GRC, the relevant Registrar General will send you a draft of the information to be recorded in the Gender Recognition Register (GRR) to clarify what the entry will look like and to resolve any queries before the registration goes ahead. The draft will contain all the details about date and place of birth and parentage that are included in your original birth record
• In the case of an adopted person, the draft will show the adoptive parents rather than the birth parents unless the adoption order has been quashed.
• If your birth was registered in England and Wales or Scotland, the format of your certificate will match that of your original birth certificate, other than it will show your new name and acquired gender.
• On receipt of your confirmation that the draft contains the correct information, the Registrar General will create a new record in the GRR. Your current contact details will not be recorded in the register. (The purpose of a GRR is simply to create a new record from which the Registrar General may produce a new birth certificate. It is not a record of all known transsexual people, nor will it be ever be used as such. The register does not record current address details or any other information which could be used to locate a transsexual person. The Register is held in the same way as the other central registers maintained by the Registrar General, such as those for adopted children and those for whom the courts have issued a parental order, and is not be open for public scrutiny.)
• A free short birth certificate will be sent to you by post together with any additional full birth certificates you have purchased. Information about purchasing a new birth certificate will be sent to you with the draft entry.
I would be amazed if there were many people who went throught the whole GRC process and then decided not to bother getting the new birth certificate when the process is pretty much automatic.