How can illegal immigrants get married in UK

Civil marriage ceremonies
Giving notice
You and your partner must give notice of marriage in your local Register Office, whether or not you wish to marry in that district. If you and your partner live in different places, you’ll both have to go to your own local Register Office to give notice. The Superintendent Registrar then issues authority for the marriage and you can marry in any Register Office or local authority approved premises in any district.
In England and Wales, 28 days notice must be given to the Register Office before the marriage can take place. You have to get married within 12 months of giving notice. Both partners must be resident for seven days in England or Wales before notice is given. A notice must state where the marriage is to take place. There is a fee for giving notice.
If one of the partners has been issued with a gender recognition certificate and was previously the civil partner of the person who they wish to marry, there is no requirement for the 28 day notice period. In this case, notice of the marriage and the marriage itself can happen on the same day.
In the period between the notice of intention to marry and the ceremony, anyone with strong grounds for objecting to the marriage can do so. Making a false statement is a criminal offence.
Documents you'll need to give notice
You and your partner will be asked for certain information when giving notice of your intention to marry. If you or your partner are not citizens of a European Economic Area country, you'll also have to submit evidence of your immigration status when you give notice to marry.
Giving false information is a criminal offence. The information which may be required is:-
evidence of name and address
evidence of date of birth
if one partner has been married before or in a civil partnership, documentary evidence that the marriage or civil partnership has ended, for example, a death certificate or decree absolute. Uncertified photocopies are not accepted. A certified copy of a decree absolute may be obtained from the court which decided the divorce. This can take about a week
evidence of nationality.
A variety of documents can be used as evidence of the information required, but a passport or travel document is usually sufficient.