Alarm not setting?

I have a Veritas R8 alarm (one pad at front door and one at the back.) the issue -as and from last night when you put on the full alarm it goes for the usual time to allow you to get away but then doesn't stop it goes on to a continuos bleeps. It does exactly the same when you set the Part. It clicks for 4or 5 times and then doesn't go silent rather the loud bleeps the same as on Full. I have reset it a number of times and also changed the code but nothing is changing. Could it be a battery issue? Also the mains electric went off briefly last week but this is a common occurrence with my country house.
Thank you.