From my own long and drawn out experience, if you want a prompt and acceptable settlement:
1. Go to Glass’ Guide for a true market value for your vehicle. It’ll give you a range of dealership prices.
2. Decide on a fair value within this range depending on your van’s spec and condition.
3. Send your request for this amount as settlement along with a screenshot of the Glass website valuation, and link to here: http://www.financial-ombudsman.org.uk/publications/technical_notes/motor-valuation.html
4. In your request make mention of Section 2 of the guidelines, referring in particular to:
“We pay most attention to valuations given in motor-trade guides, such as Parkers’, Glass’s and CAP. These are based on extensive nationwide research of actual selling prices (rather than just advertised prices).”
and
“We do not usually find advertisements for similar vehicles very persuasive. A vehicle may often be sold for less than the advertised price – and differences in mileage, year of registration, model type etc can significantly affect the value.”
I was three months arguing with insurers about their derisory treatment of me and their laughable offers last year. Unfortunately for them I already had a replacement vehicle so had the time to wait it out, and eventually stumbled upon the Ombudsman’s guidelines. I went through the above steps and a cheque for the amount I was requesting arrived the day after.
EDIT – forgot to say: tell them that if they don’t accept your valuation then you will be referring the case to the Ombudsman.