Despite high inflation, the price of used cars fell 1.5% last year, figures show.
The average price of a second-hand vehicle in 2011 was £9,018 compared with £9,155 in 2010, according to research from the Auto Trader company.
Cars up to three years old - now in shorter supply due to recent dips in new car sales - went for over 6% more in 2011 than in 2010, but the price of vehicles aged over 10 years fell by an average of 6%.
The average price of all second-hand cars sold in the London area dipped from £10,097 in 2010 to £9,504 in 2011.
As many as 16.65% of the cars sold in London were more than 10 years old.
The most expensive used cars last year were those sold in Northern Ireland, with an average price of £9,704.
Auto Trader said the overall nationwide average fall last year would have been even higher but for the fact that prices rose in November and December 2011 following seven successive monthly falls.
Auto Trader strategy director Tim Peake said: "The impact of reduced new and used-car transactions, created by relatively weak consumer demand, is leading to lower overall retail prices for used cars.
"Looking ahead, the picture for 2012 is one of a challenging market. Although inflation has started to fall, it is likely that business and consumer confidence will remain subdued. Concerns over rising unemployment and pressure on household incomes are likely to be the principle factors pinning back new and used car sales.
"The good news for consumers who are able to change their car in 2012 is that, as well as average prices falling overall, weak consumer demand means there are likely to be some really great deals around."