having found that this was also staying on all the time months ago and draining teh battery (which at first i thought was the only drain - see flat battery post ) i just removed it and was looking for a replacement one from a breaker/ebay etc...
while i was d1cking about with the alarm module, i thought i'd try it again and double ckecked that it was fooked - it was, but what i've done( which i didnt know u could do was to make a link acrosss where the relay goes in the box (R17) on the terminals shown...
the light will work as per normal car without the delay, BUT to my joy, the toad alarm also gives a 20 second delay off function to the interior light, so, when i disarm, the light comes on for 20 secs, or until i start the car, whichever is sooner

everyone is a winner