Yet the big cars have much to offer, from the mould-breaking DS of the Fifties, through the equally unconventional CX of the Seventies, to the marginally more straightforward current model, the XM.
The DS is now regarded as a design classic. That swoopy, sexy, chic shape is distinctive, with its dramatic wrap-around front screen and rounded rump. Inside, the single-spoke steering wheel and array of instruments suggests the flight deck of a Dan Dare rocket.
But a DS does not merely look the part: in its day, this Citroen was technologically well ahead of the opposition, with hydropneumatic suspension that gave a magic-carpet ride and performed the unique party trick of enabling the car to be raised and lowered. From 1968, main-beam headlamps also allowed the DS to see around corners: the alignment of the lamps was linked to the position of the front wheels.
All this makes a DS a practical classic indeed. But buying a good one is not easy, despite the fact that plenty of right-hand-drive models were built at the Citroen factory in Slough. The body panels, which unbolt easily, often reveal a rotten inner structure. You could buy a complete heap for less than pounds 1,000, but restoration costs can be horrendous.
Better to start with a decent example. A solid DS costs pounds 5,000, and pounds 10,000 (less than a dreary Mondeo) buys a pristine example. Many have been imported from France, so be prepared to grapple with left-hand drive.
Much more common is the DS's successor, the CX. It has the same suspension and no-compromise approach to car-making as the DS, but it is the front wheels that tug this huge torpedo of a car along. The Familiale seven-seaters are true avant-garde estates, with mind-boggling equipment levels. Loading the flat rear bay is easy with the suspension lowered, and the ride is smooth whatever the bulk on board. Add to the model range the highly reliable and frugal diesels, as well as the frighteningly fast GTi Turbo, and there is clearly a CX for everyone.
Looked after, these cars run up huge six-figure mileages, and tidy examples can still be had for a reasonable few thousand, but be warned: prices are rising simply because there is nothing else like them. Some of the best examples are being exported to Japan.
The XM depreciates with a vengeance, but is also the most distinctive executive car. It is much more conventional than the CX, but is quite unconventional enough for anyone used to 'normal' cars. The interior resembles the bridge of the starship Enterprise and the wedge-shaped exterior sets it apart from every other executive express.
Diesels are the popular ones, along with the heavily depreciating V6s. Top specification package is the SE, with leather, air- conditioning and ABS brakes. As little as pounds 3,000 can get you an old XM, but there might be problems with it.
The secret of successful big- Citroen ownership is to buy the right car and have it looked after by a specialist. Finding the right specialist is a matter of joining the Citroen Owners' Club and talking to other owners in your area. What soon becomes clear is that main Citroen agents have no interest in servicing even the most recent XMs. Their labour rates are usually about pounds 35 an hour whereas a smaller specialist will charge about pounds 20. Rather than being just a 'fitter', they will also understand how the cars work. A specialist can source parts direct from France, saving owners large sums of money.
The selling specialists that matter are For Wheels in Abingdon, Retromobile in London and the CX Centre in St Ives, Cambridgeshire. For Wheels is run by Paul Johnson, who has more than 18 years' experience with the marque. As a result of the CX's demise and dealers' indifference to the XM, the company specialises in the latest model. When I called, there were more than 30 for sale. Prices ranged from pounds 6,200 for a 2.0i to pounds 18,250 for a year-old automatic estate.
'Our prices are not the cheapest, but that's because these XMs have been properly prepared,' Mr Johnson says. For Wheels still finds room for the CX, of which there were 10 in stock. A 1989 eight-seater estate was on offer for pounds 7,500; at the other end of the scale, a GTi saloon that had covered 70,000 miles cost pounds 4,450.
Not surprisingly, For Wheels has a close relationship with the CX Centre and Roger Bradford, who runs it. He is passionate about CXs, and his showroom offered 20 of them, from one of the last eight-seater estates (a 1990 example, at pounds 9,250) to a blisteringly quick GTi Turbo with a 250bhp conversion (at pounds 4,250).
As for the DS, there is only one place to do your shopping: Retromobile, near Chelsea Bridge in London. Hurry there before the end of the month as its stunning collection of cars is currently adorned by some decidedly modern art. The firm offers only cars in excellent condition that can be warranted for six months. These are either well-preserved originals or models that have been properly restored. When I called they had plenty of usable cars, from 1973 DS20 with semi-automatic gearbox at pounds 5,000, to a low-mileage 1968 DS with just 30,000km on the clock at pounds 12,000. For practicality, a well-kept 1974 Safari cost pounds 6,800, while for posing purposes the ultra-rare 1967 convertible would set you back pounds 32,000.