I have seen quite a few job descriptions where fire service experience is a prerequiste or highly desirable (although they never think to stipulate in what capacity).
Quite, and it is not always a good thing. Some firefighters will have you believe that until you have ridden the big red truck with flashy blue lights and experienced as many towering infernos as they have, you can't possible know anything about fire.
That may be true when it comes to firefighting, but it certainly isn't the case when it comes to fire safety. Fire safety and firefighting are two very different things, and you don't need firefighting experience to competently carry out the former. The latter certainly doesn't entitle firefighters to think they are automatically competent at fire safety.
My advice is to get yourself on an accredited IFE accredited risk assessment course, as a foundation then gain some practical experience risk assessing various low risk premises. Depending on what course you choose will determine what level of premises you are competent to inspect.
Slowly build up to more complex and riskier premises and then consider more indepth accredited risk assessment courses if required.
Being competent means you know when something is too complex for you to deal with, and that is the time you can then look at additional training needs and attending courses to address those needs if necessary.