Why not get a bricky to do your chipping or a plasterer to tile the roof...
While some electricians maybe competent at fitting alarms many are not, some of the worst systems I have seen where fitted by electricians.
If you knew you wanted the alarm replacing you would have been better getting quotes to do this before buying and replacing the panel.
I wouldn't want to fit customer purchased kit as I can provide no warranty on it, you then have issues when it goes faulty.
People think they are going to save money by buying the kit themselves but trade don't get it any cheaper, it just limits your options really.