Bit late to the post but I had a quick look at the CIBSE Lighting Guide 13- Places of worship which was released last year and found this.
"Emergency lighting may be required in places of worship wherever there is
deemed to be a risk to the safety, health or welfare of staff and the public, should
the normal lighting fail. Failure of the normal lighting can cause three different
types of hazard, depending on the nature of the building. For all buildings, a
hazard exists if people have to evacuate the building in darkness. Emergency
lighting should be provided to allow people to safely and quickly leave the
building. The extent and nature of the emergency lighting required in places
of worship is determined by the size and complexity of the building. Detailed
guidance on emergency lighting is given in chapter 4 of this guide and SLL
Lighting Guide 12: Emergency lighting design guide (SLL, 2004)."
So I would gather from that if after a risk assessment by a fire officer the EM is deemed necessary for a Fire Certificate it would obviously be required.