Is it possible to challenge an insurance company's specialist investigation report? My partner's Audi A3 was stationary on our drive when a passerby spotted the car on fire, which was parked at the top of my drive with both my car and my partner's parents car parked behind it. I put out the fire and the fire brigade arrived shortly after and throughly investigated the fire. They informed me that, following their checks there was no signs or evidence of the car being sabotaged/attacked/set on fire - particularly as they found nothing in their checks plus they said if the car had been purposefully set on fire both my house and car and partners parents car would’ve been damaged (which they weren’t).

I’ve recently received a ‘specialist investigation report’ from the insurers who have stated the following: "The only plausible explanation for this event to occur and produce the burn pattern as witnessed would be for an accelerant of some form to be placed on the vehicle and deliberately ignited”. And also “Following the full physical forensic inspection of the vehicle it can be concluded the cause of fire is an outside influence of which deliberate ignition by person/s unknown cannot be discounted.”
Needless to say I’m shocked and disappointed given what the fire brigade told me plus I’ve had to take a loan to replace the Audi and I’ve young children so if the car was purposefully set alight - which I highly doubt - do I need to worry that it will happen again and possibly be worse than last time? I want to challenge the report based on what the fire brigade told me - is this possible?