like darren said, you need to check nearer the time, because you might have to apply for FLR, as your applying nearly 2 months before your suppose to
,,
so a couple things might happen..
1) you apply for FLR and then ILR.
2) you apply for ILR and they refuse for being too early or they keep your ILR app and they will process it when you should have submitted it (upto 30 days before you've actually been in the uk 2yrs)
so phone them maybe 2 months before your visa expires so you know what you need to do
and don't forget your 'life in the uk' test, and oh, all this will could change this year
because of changes in immigration law , so your guess is as good as mine as what you should do