C&K active 5 failure?

I came home yesterday evening and noticed the strobe on the bell box flashing but no alarm,on entering the house all appeared fine but on inspection of the alarm the tamper light was on and making a faint bleeping sound.I also noticed that none of the red dots on all three sensors were lighting up either,a friend at work this morning informed me that the onboard battery may have failed and advised a replacement which is now fitted.The Tamper light is now off with the mains and day lights lit but still no red dots on any sensors.The alarm fails to set lighting all zones and just sits there bleeping,can also reset it no problems with my code then # button.Not sure what to do now,can anyone help a single mum on benefits out as I can not afford to pay the ridiculous prices charged.