New UKBA Requirements for Settlement and Naturalisation

[Terpe]

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So, the initial visa is of course for 30 months.

Sorry to be pedantic. The initial visa for entry clearance is issued under 33 months validity.
There's an additional 3 months so that there's time for the physical relocation to UK and still qualify under the 30 months residency requirement.
At the FLR(M) application the visa issued will be for 30 months. With proper planning it's easily possible to meet the total 60 months residency requirement for ILR eligibility without an unnecessary extra FLR(M) application.
It's for this reason that it's better not to apply for the FLR(M) any early than needed as it's possible not to be able to reach the 60 month target.

Sorry Iani if you knew all this stuff but just for those readers who may not be aware.

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She entered the country on the 27th April 2013.
The visa runs out on 09/01/2016.
So, she will have been here for 30 months to meet the residency on the 27th October this year - 2015.

So am I right in thinking, we could apply 28 days before this date - say about the 30th September(ish)? Or up until the end of October?

Yes, you can apply up to a maximum of 28 days before the 30 month anniversary if necessary. Do be sure not to apply so early that the issued 30 month visa prevents meeting the total 60 months residency.
Actually, the latest you can apply is the visa expiry date.

The reason I am asking, well it's this new language requirement. Her original pass was in ESOL, which of course is now defunct, but can be used in applications up until the 5th November 2015. Be good then to get applied before then.

Yes, that's correct.
Paragraph 32D of the Immigration Rules Appendix FM-SE applies provided there is also compliance under transitional arrangements:-

Under transitional arrangements, applicants who took an approved test before 6 April 2015 may continue to rely on that test (if it was in Appendix O on 5 April 2015) to meet the English language requirement in a partner or parent application as long as they submit their application before 6 November 2015 and regardless of whether the test was taken at a test centre approved by the Secretary of State as a secure English language test centre. The list of approved providers and tests at 5 April 2015 is available on gov.uk at URL="https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/405631/selt_transitional.pdf"]Approved SELT tests - transitional list.[/URL]

I know she could pass the test in IELTS, but they have a validity of 2 years, and if she had to pass this to apply for the FLR, then it would be a bit crazy as she'd have to retake it once again before the ILR.

Actually Iani, the Immigration Rules allow for a previously awarded B1 grade pass (such as IELTS) for English Language to be perfectly acceptable for both ILR and Naturalisation applications, even if the certificate itself is expired.

Take a look here

Means your timing decisions concerning both B1 level English Language and Like in The UK test are essentially under your own control as expiration is not an issue.

Personally I always advise folks to secure both as early as possible in order to avoid any time pressures.

If you'd like to see 'chapter and verse' from the immigration rules on ILR English Language tests and Life in UK test then follow this link to the
Immigration Rules - Appendix KoLL

Just as a footnote - everyone should check stated sources to satisfy themselves that the info remains valid.