There is no prescribed requirement for signs under fire precaution legislation nor health and safety legislation, Exit signs are prescribed under Buiding Regulations Guidance and reference to BS5499 series of Standards is made. The requirement for any sign or notice is determined by the formal risk assessment. If the requirement to communicate can be acheived by management another way then that can be perfectly acceptable. There are requirements to communicate,inform,instruct,identify,locate and give repeated information about significant fire safety measures,procedures,practices,equipment and escape route. The method you chose is totally discretionary.
My personal opinion is that good signing , conforming to British and International Standard can make a major contribution to a good Fire Safety Strategy and Management System.
As I have said many times before the crap that we show over doors at the moment and in new guidance documents when you would have thought that the BRE and ODPM would be competent people in this respect. It casts real doubts about the validitity of the whole set of documents if they can not get something as simple as escape route signing correct?