How can i reset my house alarm (Texecom Premier 24 series)?

I had to remove my exernal bell box to render the walls. On removal the tamper switch set off the alarm and i had to cut the wires to stop it as my own code did not stop the alarm. I now want to re-connect, but am afraid that i will not be able to stop the alarm. How can i re-connect wires and stop the alarm sounding. The inside panel now shows as bell box tamper and the service light is lit. Can i re-set myself, or do i need engineer to reset with a special code?