anti tilt alarm go off on astra coupe turbo?

On what evidence did they base that statement?
What year is the car? If it is older, it is most likely to be the back up battery in the power sounder failing, the system senses a power drop and sounds the alarm. What condition is the car battery in?
Have you checked/adjusted the bonnet switch, another very common problem (depending on year) as the bracket gets bent.
What about the interior sensors, are they being tripped by any decorations in the car?
The simple way to find out which circuit is being tripped is to go to a garage and get the alarm activation log checked on their diagnostics.

fred
November 2009