Thanks for your responses.
Regarding the battery test; I checked the batteries at source and found they were reading something like 12.75 volts and then at the panel at 12.50volts with the tester. The read on the panel itself was about 12.00 volts ( difficult enough on the needle gauge) The batteries I put on are 3 x 110 ah lead replacing 2 x 100ah. As I thought they were giving up after 3 years, I was possibly wrong in changing them.
Checking behind the panel there doesn’t seem to be any way to turn off or bypass the alarm.