I find that hard to believe!
They say that, then they inspect it, and offer you 50P.

I find that hard to believe!
Cars are like Houses/Antiques/whatever.
They are ultimately worth whatever somebody is prepared to pay for it, there are no other rules!
If you think it is worth the money, Buy it! If you dont, dont! If there is middle ground haggle!
But if I were you, I wouldn't buy a Car from a neighbour (definitely not from a friend) as a matter of principle. Serious can of worms potential here!
(Exception! I say to owners of older cars who are facing big repairs, It is worth what it would cost you to replace it!, Not what you could have sold it for. YES it is worth spending £700 doing a head gasket on an old Peugeot as long as the rest of it is in reasonable condition and you are happy to keep it for another 2-3 years)
A neighbour of mine is selling her car. I am looking to buy it. However I think she is greatly overestimating the value.
What would be the best way to find out how much the car is worth?
The reason I ask is I tried getting the value of the car from doing a price comparison insurance qoute. Compare the market said it is worth £3385 and confused.com say it is worth £4800. As I am sure you are aware that is a vast price difference.
The car in question is
2009 Ford Fiesta Zetec
1242CC
Petrol
5 Door
Manual
Mileage 40000
there are dealers offering 09's for <£4K now