Could you confirm that if a fire panel is installed in a rented premises then is it regulation/statue that it must be maintained by the landlord in a working condition at all times?

I assume because you refer to a fire panel the premises is flats and the fire alarm system protects the common areas, it is not a rented private single dwelling. If this is so the landlord is the Responsible Person which makes him/her responsible for the fire safety in the common areas which would include maintenance of the fire alarm system always.

If on the other hand it is a commercial premises and the system doesn't serve shared space and only your demise then under the terms of your lease & by virtue of your control of the workplace as an employer it will be your responsibility to maintain.