You should register your marriage with Indian embassy or consulate nder provision of foreign marriage act 

said marriage would be valid 

Marry at Indian Embassy

- Since, you both are residing in UK , then you can register the marriage under the Foreign Marriage Act before the Consulate of India. 

-  As per this Act,  Indian nationals may apply for Solemnization of new marriage, under the Foreign Marriage Act, 1969 where at least one of the prospective bride or bridegroom must be Indian national. 

- The following documents needed 

•  application forms with four passport size photographs each of prospective bride and bridegroom.
• Passport or Identity Document of both bride and bridegroom and a photocopy thereof;
• Copy of Proof of address in UK
• ‘Notice of Intended Marriage’ and ‘Form of Declaration’ by prospective bride and bridegroom in duplicate (Form to be given by the Embassy).
• Passports or identity document of all three witnesses and photocopy thereof
• Original full page of the newspapers in which the advertisements were published

Yes, It will be legal marriage according UK laws ( UK foreign Marriage Act)

Law: Foreign Marriage Act 1892, UK

Dear Sir, 

It will be a valid proof only within India and Uk. The marriage could be solemnized between you and your Iranian spouse only after giving 30 days notice of intended marriage in the daily newspaper in India and the notice shall also be published in the one of the leading newspapers of Iran which has a broader outreach.  Then later on, declaration and a sworn affidavit shall be drafted with attestation from at least two witnesses.

These are certain other procedures that must be fulfilled by your to-be wife, they are :-

Your to wife should obtain a no-objection  Certificate from their respective Embassy/Consulate in India. In case, where the Embassy/Consulate does not issue such a certificate, a Sworn Affidavit attested by the respective Embassy/ Consulate of the non-Indian applicant needs to be submitted. A certificate from the Embassy/Consulate of the non-Indian applicant stating that his/her country’s respective law does not prohibit their nationals from marrying foreign nationals. 

If you have any further queries, kindly reach out to me,

Regards, 

Sanmathi S. Rao

No doubt to claim rights as per Indian laws you need to register your marriage in India or in the Indian consulate of the country where you reside.

If you do not want to claim validity of your marriage in India as per Indian laws,  with the given fact that you are a NRI and your spouse is a foreigner, then you may not have to get your marriage registered following the process of Indian laws in this regard. 

However the marriage certificate given by the UK government is otherwise valid to prove that you are married to your spouse. 

In the context of your situation as non-resident Indian and Iranian planning to marry in the United Kingdom, obtaining a marriage certificate in the UK is generally recognized as valid proof of marriage within the UK. However, it's essential to be aware that the recognition of your marriage in other countries is subject to the respective legal requirements as per the country.

Dear client,

A marriage certificate issued in the United Kingdom is generally recognized internationally as a valid proof of marriage. However, the recognition of the marriage certificate might vary from country to country based on their individual laws and regulations. It's essential to check the specific requirements and regulations regarding the recognition of foreign marriages in both India and Iran. Sometimes, additional steps such as authentication or registration with the respective embassies or consulates might be necessary for the marriage to be recognized in these countries. You can reach out to us for further assistance

Yes