Just found this thread and am in a similar situation. Applied for visa and entered in March. Married more than 4 years to hubby at time of visa application, but didn't have the KOL or time to do it as a visitor. Based on the info in this thread, my visa endorsement is one that just requires KOL, and then ILR can be sought at any time in the 2 years.
This was news to me as there was no information/notation with my visa to indicate this was the case. I saw the 2 yr forward expiry date, and thought, ah well, have to wait like everyone else. Now I guess this isn't so.
Just as an FYI, I sent in lots of documentation from across the 7 year span of our marriage so far, including copies of tax returns, etc. and in the covering letter, I did ask if based on the relevant provisions if I could be granted ILE subject to KOL (or something to that effect).
So anyway, I am going to swot up on my Life in the UK test book and try to take my test ASAP so I can apply for Indefinite Leave to Remain. Would the same Set M forms be used for this?