This will be no help, but there is a relay - I forget which one.
My alarm keeps it on for 5-20 seconds (programmable), but like I said there is a relay with a delay function.
I'll check the manual and see if Ican remember.
Edit # 1 - OK, I'm pretty sure its #05 in this pic. From memory its either in the kick by the central locking computer or under the dash behind the glove box on RHD models (so may be behind the IC in LHD)
Edit #2
This may help