If you are planning to get married in the UK and you are subject to immigration control while in the UK, you will need to follow new rules.
If you are a British citizen, a national of a country in the European Economic Area (EEA), or you have a certificate of entitlement giving you right of abode in the UK in your passport, you are not subject to immigration control. These new rules do not apply to you.
If you are coming to the UK from overseas to get married, you must have either a fiancé or fiancée, or a marriage visitor visa in your passport in order to give notice to marry to a Registrar.
If you are already in the UK, you will need to either have settled status in the UK, or apply to the Home Office for a certificate of approval before giving notice to marry to a Registrar.
Whether you are overseas or already in the UK, you will need to give notice to marry to a Registrar at a designated Register Office.