Do you know who installed the alarm system? As you say you can reset the alarm panel to factory settings by powering down but if the installer boss-coded the engineer code you wont get the default 1234 engineer code & would need the pcb resetting by Texecom so it would probably be as cheap to...
It may well be an easy job not if it's a rental property & you live 150 miles away.
Also I thought it was a criminal offence for a non-Gas Safe person to remove the case from a boiler, let alone service any of the parts, or has the law changed.
I've been asked to take over an Avanti system in a new build house which is a year old. I understand that Avanti is now obsolete & it's a system that I've never used.
I've managed to get a K-600HW engineering manual for the Avanti but it refers to an LED rkp whilst the system I'll be taking...