How do I disable my Laguna alarm? (Laguna 2 - 2001 model)?

I am having an intermittent fault on my 2001 Laguna Dynamique 1.8 petrol hatchback. Every now & then the alarm goes off when opening the car with the key card button & won't stop unless you leave the ca alone for about an hour or so, which is a bit of a pain. MU LOCAL Renault garage NEVER have a working diagnostic machine ('sorry sir, our machine is away for repairs.......') so does anyone know the easiest way to just turn the blody thing off? Even the AA failed to get it to stop today and he even took the battery lead off & reaconnected it!