All applicants for naturalization, including those applying to naturalise on the basis of marriage, must show “sufficient knowledge about life in the UK”, which includes passing English language and good character tests. Those making non-spouse applications must intend to live in the UK.
Applications from outside the UK will cost £1,523. For those applying in-country, a Fiance Visa application costs £1,033 or £1,643 with the Premium Service.
If you are applying with children, this charge will also increase with each dependent child.
The Fiance Visa requirements are:
A Fiance Visa lasts for six months in total, from the date of issue. During this time, you must get married to your fiance. Once you are married, you can remain in the UK for as long as your Fiance Visa is valid for example, if you had a wedding two months after the date of issue, you could remain in the UK for four month months after the wedding.