How many mA of current should I see being drawn from my battery while car is at rest, and how long does it take for the system to be completely "at rest" after removing key, latching all latches, etc?

Within 10 minutes, I'm seeing a draw of 300mA and this seems high. I wouldn't expect the security system to pull that much.

I am using a MultiMeter between the negative post and cable to measure current usage.

Thanks in advance

I'd still like to find out the answer, but I do see that after 20 minutes or so, it's only drawing about 20mA, which seems fine.

As old as these cars are getting, your liable to get variations on voltage simply from ground corrosion over time, no matter the quality of the parts. Not to mention the PO's possible custom work or lack of attention to needed work. Things to consider upon shutdown are the engagement of the temperature gauge, climate control system, cooling fan on the radio amp...etc. Combine those on and as they shut down, your draw becomes less to where you clock, radio memory, remote receiver and security system are about the only things left.
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Love the link! Thanks

Yes, the reading is fine. To get the actual final current drain, you have to take the reading after some 50-60 minutes from the car switch off and lock (and somewhat lowered further after 48 hours). This is extract from the Jaguar Service Training Course 682: