Off topic slightly but very basically and not indepth explanation of intruder grades
Intruder alarms are graded 1 to 4, Grade 1 is B&Q special, Grade 2 is what you would expect in a house and connected through a digital communicator, Grade 3 is what most insurance companies require for buisness use, using Redcare and redcare GMS, Grade 4 is banks etc (only certain companies can source Grade 4 equipment)
Intruder equipment is manufacturerd to the standards requirements for each grade.
The issue is that the Intruder system is only as good as its worst component, you could have all Grade 3 equipment but a door contact fitted as Grade 2 would mean the system is a Grade 2 system.
Hence you cant use a fire alarm power supply in a Grade 3 systems as it isnt manufactured to Grade 3 requirements or you can but its not compliant.
This isnt my problem, my problem is in fact the reverse, I cannot source a BS5839 rated power supply for a 12v Redcare GSM STU