The industry is not regualted as such, although the Institution of Fire Engineers is an organisation that Fire Engineers tend to join to demonstrate competancy, but it is not a legal requirement.
Fire alarm sytems should be designed, installed, comissioned and serviced as per the recommendations of British Standard 5839. But again, it is recommendations and not actually a legal requirement. Most of the responsibility actually lies with the people who run buildings to specify it correctly.
Fire alarm engineers do not need a certificate.
I think most of us on here would like things to be strictly regualted, but they are not.
If you want to learn more, get a copy of British Standard 5830 Part 1 2002 and read it, it is easier to read than you might think. That should cover all aspects of fire alarms for commerical premises. Domestic premises need different parts.
IFE exams are a lot of effort and probably over the top for fire alarm engineers as they cover so much more than fire alarms.
Good on you for making the effort to fid out about this.