Hi Ken
When you order a certificate, you can ask for "Reference Checking", and if the information on the certificate doesn't match the information that you give, then they refund £4 of the £7 you pay, and they don't send the certificate.
Alternatively, I think you can just give the details without the GRO reference, and they will find the right one for you for £10 (although I stand to be corrected on this).