Buzz
A lot depends on what type of door is fitted and what was specified at the time of construction
For a door to be classed as afire door it should have some form of certification or markingt o indicate it has fire resistance and that it's design has been tested to BS 476-22 : 1987
As for cold smoke seals this would have been spesified by the original design, although they can be fitted retrospectavely as can intumescent seals.
If you go to http://www.communities.gov.uk/corporate/ and follow the links for planing you can obtain a copy of Part B Document relating to fire safety in both sleeping and non sleeping premises that gives all the relevent British Standards and requirements, you will need to look at the pre 2006 Part B document

MEden - if the door was fitted prior to 1987 (as per BS 476-22 you mention) then will it still be classed as a fire door? If not, then is there a need to change the door if the door was part of a building that passed the bld reg requirements at that time? Especially if you have additional controls in place such as AFD?