Car Insurance offered total loss / written off then to repair then v low cash in lieu

Sassii

Hi All 
Your opinion, advise and help is highly appreciated 

Aviva said the vehicle deemed an insurance write off then took it for repair then said can't fix and offered cash in Lieu which I disagreed then Aviva system shows repaired but actually it's not.

Details: We have multiple car insurance with Aviva. Around two years bought Mercedes HPI class S fully working after repairing from a garage and been on road for years before buying. We never had any single problem with the car and passed the MOT last August 2020 with no issues .

Had an accident recently which, our fault and informed Aviva and emailed the photos to them and then received email from Aviva's total loss department saying ''Now that we’ve assessed the damage, we can confirm that your vehicle has been deemed an insurance write off'' and asked for more photos and car price which I answered all of their questions and provided the requested document and was happy to be written off.

After I sent to them all details Aviva's repair department called me and said they will pick up the car for repair which they done and after couple of days the garage called me saying they can't fix the car because of some sensors and blaming for some issues not related to the accident and want to link that to HPI class S of the car.
 
Aviva offered Cash in Lieu which I don't know if it's enough to repair the vehicle or not so I made a complain, which rejected, and asked them to send evidence like photos and diagnostic software printout to see if what they are taking about happened before the accident or not but Aviva replied they will not send any thing up to the cash in lieu been agreed.

Tried several times to solve that with them but Aviva didn't change their mined so I told them I'm going to take the vehicle to Mercedes Garage to be fixed on their cost and again said they will not pay any thing more than the cash in lieu been offered without VAT or my wasting time to repair the vehicle.

Policy wording
- Page 7 of the policy ''If your vehicle is lost, stolen or damaged, we will…repair your vehicle unless you notify us that you want us to pay someone else to repair it;or
pay you a cash amount equal to the loss or damage''
- Page 25 of the policy ''We shall have full discretion in the conduct of any proceedings or the settlement of any claim.''
 
Appreciate your opinion advise and help