[MarkS]

I would state that as the charging voltage is 14.6 volts, that there is nothing wrong with your regulator .
As the discharge current from the battery is less than 20mA when locked, there is no significant discharge through the alternator via short circuited alternator diodes (Open circuit diode conceivably)
So I would say there is nothing wrong with your alternator.
So I would revert back to there being an intermittent discharge from the battery, and the only one that I can think of (with the spec that you state) is the wipers.

Or search for a local supplier of goats blood !!!

PS Do you have a CD changer ? There have been reports of those spontaneously clunking away suddenly for no reason ?
And try disconnecting the Naval1. Being non-oem, I would suspect it may have been wired in incorrectly.