Hence the reason Elsa will apply for ILR in February. I also spoke with an Immigration officer at Cardiff airport - he said the visa is valid only on issued dates, not date of entry into UK. After the 2 year visa is up she must apply for 1 year ILR, then a year later, naturalization.
Quoted from ukvisas:
it is valid for the date on which you want to travel. If you have been granted entry clearance as a husband, wife, civil partner, unmarried or same-sex partner with a two year limit you will need to enter the UK within 28 days of the start date shown on your visa. You should advise the Entry Clearance Officer of your exact date of travel before your visa is issued. (You can ask for it to be post-dated for up to three months if you do not plan to travel immediately.)
http://www.ukvisas.gov.uk/servlet/Fr...=1018721067257
Just a footnote to this....the immigration guy I spoke to also stated that when Elsa entered the UK on 15 March, immigration @ Heathrow should NOT have stamped the entry date directly ON top of the visa, but on an adjoining page. Also, look at the visa, it says very clearly VALID FROM / VALID UNTIL...
Hope this helps.