You have to be a little careful with certified doorsets to a certain degree.
For example the following stipulations normally apply to certified doorsets:-
In an earlier post someone suggested, quite reasonably, to fit new fire rated hinges if the doors had dropped. Your client should only replace those hinges with exact 'like-for-like' replacements, if its a certified doorset.
If larger strips or the replacement hinges don't succeed in closing the gap your client may consider replacing or altering the doors. Depending on how the door set has been certified and by whom, it isn't just a question of asking Joe Bloggs the local chippy to whip them off and replace or alter them, as doing so will render the certification null and void.
Any alterations normally have to be done by an authorised manufacturer or agent, and any replacement doors will need to be exact like-for-like doors (complete with exactly the same ironmongery, hinges, strips and seals or glazing which were certified).
Furthermore you can't just replace one leaf at a time - some certifying bodies state that if you replace one you should replace both even if only one is damaged.
Not saying I agree with the above but I do understand why those stipulations exist, you can only certify something that has been tested in a certain combination. I've seen many get caught out by that, they think they have certified door sets when infact they haven't. It is down to the fire safety professional or RP to decide whether the above are important factors or not.