I'll go along with what kmpowell just said.
I paid £3000 for my original, one owner, oak green, 1990 valver from a specialist. At the time, I knew it was plenty of money, but when you add up the actual cost of time off work and fuel going to see so called minters before you find the right car, it makes the price seem more realistic.
I have just renewed my insurance, and they have aggreed the value at £4000. I belive that this is a realistic cost of what it would cost to replace my car if the worst should happen, taking into account the time and expence of sourcing it. If you write off a 2 year old Astra diesel, you get a payout, then you can go to any dealer and buy the exact same car the next day if you wanted to. With a 20 year old car, things are not that simple.