The performance of a regionally weighted and representative sample of retail used car dealers is measured each month in the CAP Used Car Performance Index.
The strength of the September used car market was in contrast with new car sales, which saw a downturn after three successive years of record registrations.
The top performing region was the West Midlands where a majority of dealers grew or maintained retail sales compared with the previous month. Only one in 10 suffered a fall in sales. Confidence in the coming months is also stronger in the West Midlands than most regions, despite almost universal expectations of a slowdown in retail business toward the year-end. Only 30% of dealers there were expecting to sell fewer used cars during October.
Also continuing a successful trading run were dealers in Scotland, who turned in the second best results in the September survey. North of the border 67% of dealers increased sales, with 11% maintaining level performance and 22% suffering a fall.
Dealers in Northern Ireland came in third with 60% enjoying more sales, 10% maintaining performance and 30 per cent seeing a reduction.
The worst results were reported by dealers in the East of England, the South West, Yorkshire and Humberside. In the latter two regions half of all dealers questioned sold fewer retail used cars in September compared with August, with 38% in the Eastern region reporting worse results. Dealers here reported the lowest confidence in used car retail sales moving into October.
Daren Wiseman, managing editor of CAP Black Book, said: "September is typically the last of the very busy months for retailing used cars. The confidence projections from this survey show that dealers are now generally expecting business to quieten until the usual upturn at the start of the New Year."