The only way to that is to buy the certificate. Do you have a problem in looking up the record of birth from the GRO? The local library can help with this or an LDS study centre, BMD in conjunction with the census. Sometimes the baptism shows the date of birth, and baptisms are sometimes on IGI (in your case I have looked and that's a problem), or otherwise on parish record for the church, which are at the County Archives, or sometimes in a local library, say Winchester, Southampton or maybe Bournemouth.
You could do this yourself, or employ a researcher, or maybe someone would offer to do it for you.
Tom