After tripping out the power supply to the alarm unit and re-connecting mains power the Buttons on the control panel do not work.

Power is reaching the unit and the Power and Dat lights are lit up.

Any suggestions as to how I can restore the unit to working order?

Could it be an internal fuse or something?

After tripping out the power supply to the alarm unit and re-connecting mains power the Buttons on the control panel do not work.

Power is reaching the unit and the Power and Dat lights are lit up.

Any suggestions as to how I can restore the unit to working order?

Could it be an internal fuse or something?

Normally this is down to a faulty battery.

Down power the mains (be careful, main voltages are dangerous) and internal battery. The external sounder should sound.

Power up on mains only is the panel responding? If so go buy a battery and replace.

If not you may have a cable or equipment fault (tamper).

And check the back of the pcb if the battery is older that 4 years, if its burnt and black you need a new panel