bmw 318ti proximity sensor location

I am away to install a Clifford concept 300 into my 1995 BMW 318ti. where would be the best location for the proximity sensor? Thanks Richard

Roof lining behind dome light fitting or adjacent gear shift or under rear ashtray. Roof lining is best, adjust before securing by turning pot to min then bring it up a fraction.

Sorry, every other car I do these days is a BMW of one sort or another,yesterday, I did an '84 Mini!!! What a rotten piece of garbage, it cost the owner real money and he was spending over £1000 on the bodywork, threw a wobbly when I told him I replaced a door contact switch because it was rotten, glad I didn't mention the rest of it. Any way your suggestion is the best, its a squeeze, just drop it to the panel, there's no room to stick it to the roof motor; now read this:- take one  relay, use the aux output that you can set to activate when you arm the alarm (grey/purple), feed it to 85, 12v+ at 3 amps to 87 and 86, 30 via two 1N40xx series diodes bars away from relay to lock and unlock. Set that aux to timer for 3 secs. This will deadlock the car when you arm the alarm but not when you ign autolock. If you take a second relay from the other aux (grey/blue), wire the same way but only feed to the lock wire and set it for 15 secs this will give you window and roof close whenever you hit the bottom right button.