Hi Lewis,
Don't forget, that right hand driven cars are only interesting in the UK within Europe. Means that all comparisons to prices on the continent are maybe wrong - a right hand driven car don't brings up the money on contintental Europe.
As Daniel mentioned, value is dependent of condition, year of manufacturing doesn't matter that much. Cars in original shape are more worthful in the meantime, tuning excesses of the 1990s put pressure on price.
If you could show some pictures an estimation of price would be easier.
LeCar5