Might not be the same thing, but my gf's fezza zetec s had batt drain too,
Turned out the electric fan was staying on too long
When leaving the car, hence draining the batt,
I had to climb through the boot to pie the doors as key wouldn't open the doors
By remote, also the damn thing is de locked, which is why I had to go
Through the boot lol

Anyway changed the fan relay, had been ok for a few months now recently
Done it Friday just gone ��