I had the same issue with a classic mini. After continuously not accepting the valve nor that it was a write off I they put me directly in touch with the pre accident valuation specialist who provided the validation. I prepared a portfolio of information including pictures, work completed, evidence of the validation of similar cars for sale as well as written feedback from the mini register. After several conversations with the insurance specialist and a re inspection I did get the value increased to 2/3 of what it was actually worth. In the end I accepted I had enough to cover the repairs and