I would also add that for credibility you should consider getting third party accreditation, as recommended in the BS.
Your qualifications at the moment don't distinguish you from my local plumber who according to his sign written van is also competent to maintain your fire alarm system........hmmmm!
Seems sensible. But what if the the 'third party accreditors' don't/can't do their job properly? So do the 'third party accreditors' also get accredited by a 'third party' and so on ad infinitum? In the end we could all be double-checked for ability and competence to such a degree that the costs in doing so will make the cost of doing any work prohibitive. Are we talking about just creating 'jobs for the boys' and, if so, where does it all end? Could we be making the costs to carry out work in this industry so great, that no start-up businesses could afford to work in it, to the benefit of the established businesses and to the disadvantage to the customer in increased costs?
Is there not a case for saying that fire alarm works are covered by a clear and sensible (!) set of recommendations and a legal system for punishing wrongdoers, that if properly enforced, would mean that eventually no one would dare not to design,install, commission, service to these recommendations because the punishment is so great?