Wiring Renault espace?

The battery on my renault espace keeps going flat, i've had the battery and the alternator checked and they are both fine.
It doesn't happen all the time, about once a week, but after a jump start, it's fine again, then one day i'll park up and within about 2 hours the battery is dead, not even the clock works, something is obviously draining it, any idea's as to how to find the fault would be great, cheers, Tom