What you think may be illegal, or immoral, isn't necessarily enshrined in law?
If you marry today at at Register Office, you must provide proof of identity, address, and age.
A passport suffices. A birth certificate is also good, but not actually required!
If you marry at a church, the incumbent just has to be satisfied as to your identity.
He/she may require proof such as certificates; he/she may not.
As I keep saying: under English Law you have the right to call yourself anything you like, just as long as there is no attempt to defraud or deceive.
Getting married under an assumed name does not fall into either category!
In years past, there was even less need to provide proof of identity.
E.G. very few people had a passport, or driving licence, or even knew where there birth certificate was!!
