Accenta 8 intruder alarm system?

After a mains power cut a few days ago, the internal sounder on the alarm system didn't sound any more when the alarm was being set or un-set or when triggered, although the external sounder and strobe still worked. I switched the mains power off and replaced all the fuses in the panel, and then put the power back on, to no avail and now the remote keypads are not functioning or showing red and green power lights at all and we cannot now set the alarm. I switched off the power to the system and removed the battery, and switched the mains power back on, at this point the full alarm system started sounding and would not reset with the keypads, I then switched off the mains power to the system, with the battery still removed, and the external sounder and strobe were still sounding but the internal sounder was not. The system would not re-set or stop sounding from the key pads and so I put the battery back into the box and re-connected it and the alarm stopped sounding. However, there are no red and green indicator lights lit up on both key pads and the alarm will not set, the keys seem to be not working any more. There must be some power getting to the key pads because the background glow behind the push buttons is lit all the time. Any help in getting this system working again would be greatly appreciated.