You are right - Fire Safety can only be dealt with under the Order, licensing and registration bodies cannot impose conditions that relate to fire safety.
Oh really ?
If - as a condition of registration - the applicant if required to comply with the following (extract from OFSTED Standard 6 - Safety) then it looks to me as if OFSTED have a fire safety enforcement role
Fire safety
6.11 A fire blanket, which conforms to BS EN safety standards, is provided
in the kitchen.
6.12 Smoke alarms, which conform to BS EN safety standards, are provided
at every level of the house and are maintained in working condition.
6.13 The childminder has devised and practised an emergency escape plan.
6.14 If a local fire safety officer has visited, the childminder complies with, and
keeps records of, any recommendations he has made.