Just Bought a brand new battery, the car was.

No way of knowing what drained the battery (over the internet). You need to have someone check it out.

Double check that no interior lights or other accessories were left on, otherwise that might not look too good when you bring it to a shop.

There are lots of Control Modules that need to "fall asleep" in order for there to be no excessive current draw that will drain the battery.
Maybe one or module is staying awake for some reason.

Thomas