Hiya Suey, If I have understood you correctly I suspect that the certificate you have is a copy of one prepared by the Registrar of B, M & D from details in the marriage register. So the writing on your certificate is that of the Registrar which is why the writing is all the same. If you look at the marriage register of the appropriate church you will almost certainly see that most of the writing is in the hand of the clergyman but the bride and groom and the witnesses would (or should have!) signed the register themselves or made their mark. I hope this helps
