Ok here is what UKBA state:-
Where an applicant has satisfied all of the requirements for Indefinite Leave to Enter (ILE),
except the KOL requirement, they should be granted 27 months Leave to Enter (LTE).
During this time they can, at any point, satisfy the KOL requirement in the UK and apply
for Indefinite Leave to Remain (ILR).
Source:-http://www.ukvisas.gov.uk/en/ecg/settlement/knowledgeoflanguage#21490059
So it seems as soon as you have passed life in the uk test you may apply for ILR
Where did you apply for the visa? was it European area?