IN PRINCIPLE, the idea of Motorail is perfect. You present yourself and your car at Calais or Dieppe. The car goes on a transporter, while you are accommodated in first- or second-class sleeping compartments. The train crosses France at night while you sleep: in the morning, you arrive refreshed at your destination and drive the car off to begin your holiday.

However, for a service that sells itself on speed, it can often seem to run at an infuriatingly unhurried pace when it comes to loading and unloading cars. The accommodation on the Motorail train is good but fairly basic, even in first class. If you are a light sleeper, you can expect a disturbed night: the train rattles about considerably, and often comes to a halt for no obvious reason. Washing facilities are basic.

Take plenty of mineral water and lots of edibles; food on the train is sometimes available from a self-service restaurant car, but it is not brilliant.

However, despite the problems, there is much to like about Motorail. Even with all the unexplained delays and the lack of efficient organisation during the unloading process, having the car carried to the south of France gets you to your holiday destination quickly - and spares you the labour of a long drive.

There are particular attractions for people with young children, and for those with elderly cars that they do not want to risk on a long, hot motorway journey. Also, any excuse to gaze at France from a train is an opportunity worth taking.

Motorail, however, is not necessarily a cheap way to travel. A return trip from Calais to Brive for a family of four costs from around pounds 700 including the Channel ferry crossing and couchette accommodation. There is no question that it would be far cheaper to drive down. Even if you ate at good restaurants and stayed at an expensive hotel you would still probably end up paying less than the Motorail fare. But that is not really the point. People do not seem to use Motorail to save money. Many people do it for no better reason than that they like it.

Motorail routes from Channel ports

Calais to: Avignon; Biarritz; Bordeaux; Brive; Frejus/St Raphael; Moutiers; Narbonne; Nice; Toulouse.

Dieppe to: Avignon; Frejus/St Raphael.

There is also a wide choice of Motorail services from Paris, Lille and Nantes.

Further information: French National Railways (SNCF) has special discount cross-Channel fares with Brittany Ferries, Hoverspeed, Stena Sealink and P & O European Ferries. Railsavers (0253 300080) offers discounts on Motorail for travel in the UK and on the Continent.

Motorbikes: Motorbikes are transported on all routes within France.

Bicycles: These must be transported inside your vehice. Bicycles carried on specially designed roof or boot racks will be refused on Motorail and will be forwarded as registered luggage on the next available parcels train (subject to a handling fee and delivery within five days).

Further information: Motorail brochures are available from high street travel agencies or direct from SNCF, 179 Piccadilly, London W1V 0BA (071-409 3518; fax 071- 409 1652; brochure requests 071-499 1075).

Air France Rail

FOR holidaymakers to France, this is one of the best deals on the market. Air France has teamed up with SNCF to offer a combined fare to any destination on the French rail network. A return ticket from London to Dijon, for example, costs pounds 139 including a flight to Paris and a TGV high-speed train journey from Paris to Dijon (the child fare is pounds 89). For an additional payment, you can fly to Paris from Birmingham, Bristol, Edinburgh/Glasgow, Manchester or Southampton.

The Air France Rail deal also allows travellers to combine a return flight to Paris with the SNCF Euro-Domino unlimited rail pass: a flight from Bristol, for example, combined with a three-day pass (three days' rail travel in a one month period), costs pounds 215 for over-26s, pounds 198 for 21- to 26-year-olds and pounds 131 for 2- to 11-year-olds.

Further information: Air France Rail reservations 081-571 1413; 071-499 1075 for brochures.

Euro-Domino Rail Pass

THREE days' unlimited rail travel in a period of one month cost pounds 102; five days pounds 141, and 10 days pounds 221. For under-26s the pass costs pounds 84, pounds 124 and pounds 194 respectively. Available from SNCF.

Further information: Information and bookings for rail travel to France available at the International Rail Centre, Victoria Station, London SW1W 1JY (071-834 2345 inquiries; 071-828 0892 credit card bookings). Bookings and inquiries can also be made at selected British Rail stations and travel agents.