When there is an incident at any UK airport , the airport emergency services are only required to take the initial action.
Their equipment is designed for a short sharp strategy.
The way any UK Airport , even Heathrow , deals with any incident depends on the availability of outside services to continue emergency action when Airport services are depleted.
So, although the Airport Firemen will be in place , the airport emergency plans cannot be effected.
While I suppose , theoretically , the Fire Category remains the same , the Airport will not be able to put their emergency plans into action and the airport licence may be breached.