If not a requirement it is certainly desirable to have trained and certified contractors fit fire resisting doors. I have recently experienced poor workmanship in new installations, smoke seals missing, glazing not FR and door closers not correctly fitted. A fire resisting door comes in a door set and includes the frame and door furniture, nothing additional should be added as it may affect the integrity. There is also the matter of sealing the area surrounding the frame with FR materials. The installers need to know what they are doing. There are third party fire door certification schemes and if you use one of the web search engines you will find them. I would suggest contacting the manufacture of the doorsets for their view.

http://www.bwf.org.uk/firedoors/ Some useful information here.

I'm a fire risk assessor but not a joiner. How do you think a good joiner would react if I tell him his fire doors are not fitted correctly? Better to have a competent joiner in the first place.

Thanks all for your comments most are what I had thought. Apparently the friends partner was on a site about to hang the doors when he got told by the architect that the person hanging them needed to be certificated. As you can imagine he was not best pleased but wanted to check if this was something he should have if it was now a requirement. Looking at the links provided it would appear that it is the doors that shold be certified but a qualified joiner should be able to fit them as people have stated.

You may find that the requirement has come from the client's tender spec?