Under BMW direction, Rover has been marking time as far as its upper-range saloons and coupes are concerned, but only until the single replacement design for the present 600 and 800-series cars, with a certain amount of retro styling, appears. That was expected to be later this year, but the indications are that the launch has been postponed until 1999.

Sales forecasts for the new car will almost certainly be much higher than the 600 and 800 have managed jointly in the last few years. While they have been left pretty well to look after themselves, there is no doubt that a major marketing push will accompany the new car's arrival.

Rover has taken to slipping in new variants of the existing cars from time to time, in very low-key introductions which no longer seem to involve any invitations to drive. Most recent replacement models were the rather oddly titled 600 iS, iSD, iL and iLD, superseding the 618i automatic, 618Si and 620SDi.

The ''S'' cars take a sportier approach, being fitted as standard with 16in alloy wheels, while the ''L'' specification types offer a more luxuriously appointed interior with full leather upholstery and trim, plus extra wood inserts. They come with either the 1.8 petrol or two-litre diesel engines familiar from other cars in the range.

Not much changes in the 800-series, which is still a handsome design, even if - unusually - the saloon seems to score higher style marks than the coupe.

While there have been few alterations to the 800's suspension set-up, it does have the benefit of a fine engine at the top of the list, the 2.5-litre KV6 development of the highly regarded

K-series which appears in smaller vehicles throughout the Rover catalogue.

Sterling is the model name used for the more luxurious 800s, with whatever engine specification. Vitesse, first used by the original Rover company back in the Thirties, is the one for the two-litre

turbocharged types.

Built in quite small numbers, Rover has three ''niche'' models, based on one-generation-back designs, but recently upgraded.

The 1.6-litre Tourer is the company's only estate, the 1.6-litre Cabriolet is its only mid-range convertible, and the smaller coupe (without a model number) has the advantage of being available with the ingeniously enlarged 1.8-litre VVC version of the four-cylinder K-series engine.