Thanks very much Gavin, this is helpful!Not personally aware of any but was told by a fire safety officer in Bath (avon and Somerset fire and rescue) that they are discussing the risks and there was suggestions that BESS should be registered with the fire service so that they are aware that in a fire the batteries could be in the building. WHen going to propertieds with solar pv they will assume until proven otherwise BESS is present. He said he could foresee a scenario where the BESS must have an external firemans switch so that in grid failure or fire they can cut off the battery generation inside the property from outide before going in.
Same fire officer also said that if they were in the loft and caught fire the fire serevice would almost certainly refuse to enter the building (unless resuing people) to try and put them out due to the weight and crashing through floor but also accessing them to put out a lithium ion fire is goign to be difficult. woudl likely lead to your house buring down and they would look to only prevent the spread to neighbourign properties.
the register of battery installs would allow them to know of any risk if going in a house and the fire spreading to them and quickly getting out of control .... seems sensible idea.
Your best point of contact would be individual fire services - maybe the press or fire safety teams.