Hello I have recently carried a one day coarse set out by the BRE in which it allows me to fit and repair firedoor. Is this certificate any Good as my employer put me on it and now have told me not to fit anymore doors. 

Strange to put you on a course, then don't allow you to take advantage, but knowledge is always useful and you may be able to use it in the future.

I'm guessing it was this: http://www.bre.co.uk/eventdetails.jsp?id=15147

Seems to give you the required competence as would be required by legislation. Perhaps your employer or their clients need a third party certified repair & install service?