KEEP a watchful eye on the throughput your local car auction centre - there are bargains to be had among the nearly-new, high-mileage sector of the used vehicle market.

And that's because many fleet sellers are expecting too-high prices for such vehicles, so they do not sell at auction first time out.

This is when the prospective private buyer can cash in - the same unsold cars will then come back into the auction centre's offered lots, possibly up to several weeks later, but almost always with a much lower reserve price.

So there is the need to track unsold vehicles, but the extra effort will pay dividends.

The clue to all this comes in a warning from the Society of Motor Auctions (SMA), which says that ex-fleet vehicles are not selling under the hammer because many fleet operators insist on inappropriately high reserve prices.

The SMA, part of the Retail Motor Industry Federation, says that some vehicle stock has remained on members' books for more than 100 days, despite being repeatedly offered for sale.

Alistair Manson, SMA director, said this insistence on high prices was both unrealistic and uneconomical, "as unsold vehicles often sell for less than the first bid many weeks later". There you have it: prices will tumble as top dealers certainly will not pay daft amounts for cars with too high a mileage, so a bargain set of wheels could easily be yours. Meanwhile, buyer advice website UsedCarExpert.com says there are affordable second-hand cars out there that can satisfy the craving for a premium badge.

The online operation's Matt Tumbridge said: "If you long for a car seat that is a little more like an armchair than a bus chair, it is time to upgrade to a more serious car. You will need a fully-fledged, grown-up executive saloon, so here are three of the best that are now affordable on the used market:"

  • Audi A6 (1998 on) - The Audi easily matches the BMW 5 Series and Mercedes E-Class for quality and all-round ability, says Tumbridge. It is arguably better-built inside and out, but the Audi badge does not have the image, so that means lower prices. This is probably the stand-out bargain used buy of the three cars listed here, he adds.

Most economical model is the 1.9 Tdi 115, which returns 52.3mpg overall, and best used buy is the 2.4-litre V6 - a big engine yes, Tumbridge points out, but it has decent power and, because it is petrol, they come much cheaper.

UsedCarExpert.com lists 15 pre-buy checks, and says among the classified adverts will be found year-2000, or W or X-plated, 2.4 V6 examples of around 70,000 miles' use for just over the £5,000 mark.

  • VW Passat (1996-2004) Roomy, well finished, and cheap to own, maintains Tumbridge. On the used market it is also the bargain of this group, and it has good engines and better specifications and models from 2001. There are lots in circulation, so there is wide choice - but it won't turn any heads.

Most economical model is the 1.9 Tdi 115, which returns a combined-cycle 53.3mpg, and best used buy is either a 1.9 Tdi SE, or 2.3 V5. UsedCarExpert.com recommends 22 buyers' checks, and adds that a 2000, or W or X-plated 2.3 V5, again with 70,000 miles, will sell privately for around £3,280.

  • BMW 5 Series (1996-2004) - "Brilliantly engineered and built.