What price would you expect to pay if you bought a car in the same condition as yours from a dealer?
I look at mine,then look at whats for sale at dealers,and private around the country,then add £1000 just to be safe!
Some ins companies will do a reinstate as is policy,"wont get written off so easily" as well for an extra 25% or so of the premium!
My current multicar policy with FJ allows me to self value each of my 3 cars up to £15k,anything over needs a club valuation certificate!
They will require recent photos to back up your valuation every 2-3 yrs.