Average part-exchange stock sold at auction increased by 12.7%, up £346 in May, according to Manheim’s latest market analysis.
The April to May figure also recorded an increase for average part-exchange values by 2% or £61 to £3,077.
Average mileage decreased by 511 miles between May 2013 and May 2014, while the month-on-month results actually showed an increase of 1,021 miles. Vehicle age remained consisted at 101 months.
Daren Wiseman, valuation services manager at Manheim Auctions, said: "Record-breaking new car figures around the plate change in March have been followed by strong used car progress as well.
“This has led to an increase in quality product in the wholesale market, providing buyers with far more choice, especially when it comes to the newer, low mileage stock.
“There is a danger of a build-up of unsold stock should such strong growth continue; however, with a softening in values and stabilisation in retail demand, it is likely that the market will return to its seasonal norms over the coming months."
The average selling price for five of the 10 segments analysed actually rose between April and May. This was most notable for MPV models, which rose in price by £472 or 15.6% (to £3,499).
The average age for this segment fell by five months while the average mileage saw a drop of 7,883 miles. The MPV segment also saw a rise in value year-on-year, increasing by £844 or 31.8%, which is reflective of a fall in mileage of 7,841 miles and a drop in age by three months.
Executive models experienced a rise in value month-on-month of £406 or 7.9% (to £5,570). This was in line with a fall in age of three months and a 2,451 decrease in mileage.
The biggest fall in value month-on-month was seen in the small hatchback segment, where average selling prices dropped by £107 or 4.7% (to £2,189). This fell in line with a two month increase in age, while average mileage rose by 1,557 miles. Year-on-year, however, small hatchback values were up by £139 or 6.8%.
Wiseman said: "As we predicted at the start of May, selling prices - for the most part - stabilised throughout the month and will continue to do so over the summer.
“There will be the usual seasonal pricing shift, coupled with the effects of the World Cup on retail demand; however, it looks like we could be in for a positive holiday season for the UK new and used car market."