Thanks for your helpful and constructive response.
Firstly, the company were not random, they were the closest to my house and therefore in my (proven wrong) opinion were maybe the likeliest to turn up given that at the time I called them all I had an alarm I wasn’t using going off every hour the night and was not sure what the options were.
Secondly - in parallel I was exploring the route I needed to go down to fix the alarm as we had always wanted to use the alarm but as it had been triggered by our cats we stopped setting it. In researching broken alarms I found a wealth of helpful information some of which led me to believe I should give it another go and therefore fixing it might make sense although replacing the entire thing may be more cost effective.
I restore HiFi amplifiers and components in my spare time and never ‘poke around’ with meters , I would suggest that you probably should avoid that as well, you will find it’s not good for you or the things you are ‘poking’
The alarm now seems to be working, I had to replace the main battery, two sensor batteries and a 0.25a fuse.
I can at least set and trigger it both with sensors and anti-tamper switches
Risco have provided me with a source for a keypad as well as advising which type I required.
I have also tracked down the original installer whose company unfortunately closed after a family death.
My aim will be to get it all working then get it checked and under an annual maintenance contract. I do however enjoy repairing things myself
I’m not sure which of ‘buying batteries’, ‘taking the keypad apart’ ,’poking things with a meter’ and ‘calling installers’ led you to believe I hadn’t made my mind up as I thought it was perfectly clear- I was seeking help/guidance from the forum which was why I posted in the first place.