if my math is right you are getting 7 hours of sleep.
i would not consider this an insomnia at all... that's normal, healthy amount of time.
i certainly would not be able to fall asleep early, if i slept until noon.
as others have suggested you simply need to re-adjust your sleep cycle. either skip one day and sleep for 2 hours only i.e. 5-7 am (i know it will suck big time).. but it might make you much more sleepy the same night in the earlier hours.
exercise is very important.
go for a 45 minute walk an hour or two before you plan to fall asleep.
try natural remedies such as l-tryptophan and/or melatonin.