volvo S80 1999. . .where is the immobiliser located ?

[ChantelleM]

Hi all

I have a volvo S80 2.4 SE 1999 on a T plate
I have unfortunately lost both sets of keys and the guy who came out cannot find the immobiliser anywhere,
if I dont find it Im going to have to go to volvo which is going to cost me £500

would anyone happen to know where it is

thanks

chantelle x