Years and years ago my DH was turning left out of a junction onto the main road. There were cars going in the opposite direction, but his side was clear so he began to pull out.
At the exact same moment, some eejit decided to overtake the lorry on the other side of the road and collided with my DH.
Obviously you are not supposed to overtake on a junction and the road was clear the left so we denied liability, as did the other party.
We were absolutely shocked when the insurance company came back with the decision that DH was absolutely at fault. There argument was that because the damage was to the front of our car, but the side of the over takers car, DH had hit him - even though he was already committed to pulling out when the guy overtook.
We did appeal though and in the end the insurance agreed to go 75% / 25% (in his favour still, but at least it was something).
Go back and formally appeal to your insurance company, highlighting the pictures which show the damage to your vehicle is on the side. Also tell them that CCTV footage is available and you expect them to seek it.
Also - you are entitled to access any CCTV footage the gym has of you in which you are identifiable. Those GDPR rules the gym are trying to hid behind is exactly what give you the right to access the footage.
You need to put in a subject access request for it - do it quickly as they may only keep the footage for a short amount of time. If your insurance company still refuse to also request the footage, tell them that you have and you will not accept any decision until that process is complete
ico.org.uk/for-the-public/home-cctv-systems/#rights
From Google AI:
Steps to Request Footage
Identify the Data Controller: Look for signage near the camera that includes a contact number or company name.
Act Quickly: Most businesses only retain CCTV footage for 30 to 31 days before it is overwritten.
Prepare a Written Request: While you can ask verbally, a written SAR provides proof of your request. Include the following:
Specific date and time of the incident.
Exact location of the camera.
Description of yourself and what you were wearing to help them identify you.
Proof of identity, such as a copy of your passport or driving license.
Submit the Request: Send your SAR via email or a traceable postal method like recorded delivery.
What to Expect
Response Time: The business must generally respond within one calendar month.
Redaction: To protect the privacy of others, the business may blur or pixelate other identifiable individuals in the footage.
Cost: Requests are usually free, though some organizations may charge a small administrative fee in rare or complex cases.
Third-Party Involvement: If the accident involves a crime, the police can request footage directly. For road traffic collisions without police involvement, your insurance company or solicitor can often handle the request on your behalf.