I see some small files nex to the .mlv extensions as .M00
One of them is quite large 1.5GB when the .mlv is 4.1GB
do i need that and why is it on the card taking up so much space?
Yes, you need them:
http://www.magiclantern.fm/forum/index.php?topic=11454.msg145501#msg145501 (http://www.magiclantern.fm/forum/index.php?topic=11454.msg145501#msg145501)