Help! MINI JCW 2010 won't start after refilling oil

[straddle]

Hi, I recently did a routine check of the oil on my Mini Cooper John Cooper Works 2010 having not done for ages. I noticed the oil was incredibly low - so low the dipstick could not provide a reading as it seemed to be off the bottom. This seemed odd to me as I would have expected the car to have warned me that the oil was this low. I refilled it with oil and it kept taking more and more, while I periodically checked the dipstick. I eventually added around 2L of oil before I could get it to read between the markers on the dipstick. This was two days ago. I didn't use the car yesterday but today it won't start... The lights come on but pressing the starter shuts everything down and it doesn't turn over. I'm worried I overfilled it! Could this be the cause? Recently I had noticed that the starter was firing slower than normal before I refilled the oil so it might be something else...

[E-bmw]

Oil level has nothing to do with it.

Sounds like the battery is stuffed, charge it overnight & get it checked out/do it yourself if you have a multimeter.