My insurer has declared my car a write off following an accident that was my fault (with no other vehicles involved). I am concerned that the market value they've quoted for my car appears low. I asked them to share their assessment of the value so that I can be confident it is fair, but they said they can't send me anything and that the value is based on Glasses Guides and the experience of the file handler assigned to my claim. I am looking to challenge the valuation and have looked online for price guides but am concerned that my insurer will say they reflect the retail value of the car. Other factors which the insurer said decreased the value of my car included it having failed previous MoTs and the fact that the car has not always been serviced at a main dealer. Are these factors fair ways to assess the value of my car? And do you have any other suggestions for ways I can challenge their valuation of my car?