You can drive to the Dordogne in just a day from the Channel, if you are determined enough. Head first for Paris, even if you are starting from a Normandy port. You will be going due east for quite a while, but it pays off in rapid motorway mileage. If you need a night near Paris but do not want to tangle with the metropolis proper, stay at the jolly Gros Marronier in the quiet, smart hamlet of Senlisse (if you can find it). Orleans, on the Loire, is decision time: will you head south-west on the A10, or directly south on the A71?
For the lower reaches of the Dordogne, you can follow the A10 almost to Bordeaux. On the way, you will pass through the heart of Loire chateau country, so there will be plenty of appealing places to stay if the need arises. It is then a pleasant potter upstream from St Emilion to Bergerac.
For the central reaches, head south from Orleans through the watery Sologne. At Vierzon, on the Cher, your route now goes right, taking you along a mixture of traditionally dangerous routes nationales and upgraded motorway towards Limoges and the first foothills of the Massif. But if a diversion is called for, take a side trip to Bourges, a neglected gem.
Alternatively, if you want to dawdle (and have a lot more fun), first, get yourself an atlas at a scale of about 200,000; my favourite is the wire-bound Michelin (pounds 12.99). Cross-country routes from Calais, Le Havre and Caen converge on Alencon, surrounded by grand forests and some of Normandy's most compelling landscapes. Proceed as fast as the N138 will take you to Tours, one of the most captivating of the Loire towns and the gastronomic capital of the region, with Michelin stars in galactic profusion.
For more intimate scenery, take a diversion up the Cher; the Chateau de la Menaudiere at Montrichard is my favourite affordable excursion into the world of chateau hotels.
Now your atlas really comes into play. Leave the routes nationales behind, and take to the yellow and even the white roads. My preferred route goes Le Blanc, Bellac, Rochechouart, St-Yrieix, culminating in a glorious drive past Hautefort (preferably in the late afternoon sun) before dropping into the Vezere valley. Really determined dawdlers might consider looping around to the east of Limoges instead, through the scenic departement of Creuse.
Provided you avoid travelling on the frantic weekends at the beginning and end of August, the autoroutes towards the south of France make a painless start for a trip to northern Italy. For gastronomic treats, aim to stop in Burgundy or around Lyons - perhaps even staying in the modest Relais St Martin in Collonges-au-Mont-d'Or, and eating extravagantly chez Paul Bocuse.
The Franco-Italian Alpine frontier is breached at countless points. Go through the Mont Blanc tunnel for speed (or if you want to stop and include the world's most spectacular cable-car ride from Chamonix). Drive over the Col du Lautaret if magnificent glacier scenery is more to your taste than zooming along in the dark. Then head down to the Ligurian Riviera and enjoy one of the most dramatic motorway drives Europe has to offer, along the coast to Pisa.
You might, however, prefer to take your time and loiter through the magnificent mountain scenery. In the summer, especially, there are no Alps like the Swiss ones. Go via the blissfully under-used motorways in eastern France to Strasbourg, cross into Germany to get to Basle, and thread your way into the mountains to spend a night in Grindelwald, beneath the towering north face of the Eiger; if you need to find a bed for the night you could hardly improve on the dinky new Bodmi for perfect peace.
Stick the car on a train from Kandersteg to get through the mountains to the Valais (and on into Italy if you do not want to tackle the Simplon pass). Race across the plane of the Po to Bologna - a grand medieval/Renaissance city, too often overlooked by tourists. Florence is now directly south, over the Appennines; the motorway is scarcely less scenic than the three or four alternative routes, and about five times as quick.
You'll probably hit quite a bit of traffic congestion on a trip to Vienna but go straight on at Cologne before veering south, and you skirt Frankfurt and a series of Bavarian cities - all of which, as Michelin would say, merit a detour: Wurzburg, Bamberg, Nurnberg, Regensburg. Stray a bit further and you could explore the scenic Frankische Schweiz, leading to cultural hot-spot Bayreuth, a good place to break the journey.
If you've got time to spare, heading south from Cologne takes you roughly along the course of the Rhine, but almost always at a distance from it. Koblenz to Bingen is a good stretch to look at more closely. If an early stop is indicated, make it Heidelberg: there are few more atmospheric spots than this historic university town. Leave the Rhine at Karlsruhe unless you are irresistibly drawn to the Black Forest. Ulm makes a pleasant stopover, but you will probably want as much time as possible for the artistic and cultural delights ahead in Munich and Salzburg.
Standard summer fares on the short-sea crossings are cut by 20 per cent on Hoverspeed, P&O, Sally Line and Stena Sealink. Stena has cut its Southampton- Cherbourg fare by 25 per cent. Britanny Ferries has a return fare of pounds 100 for a car and five passengers on selected crossings in the western Channel. Le Shuttle is giving away a fuel voucher worth Fr440 (about pounds 55) to full- fare motorists.
For most of the present Channel crossing bargains you must book by 31 July, although Britanny Ferries' deals expire next Saturday and Hoverspeed's extend to the end of August.
Youth and Sport have their very own government ministry in France, and this summer it is busily organising sporting activities on the autoroutes (or, at least, at 60 of the rest areas). The idea is that motorists will be persuaded to break their journeys, tempted by a choice of sports from badminton to boating. Until the scheme ends on 27 August, look for the sign saying Etapes Sportives.
If you make it as far south as the A8 near Cannes, you can visit the Musee de l'automobiliste on the motorway near Mougins, open daily in the summer from 10am to 7pm.
Roman remains in the French Pyrenees, and the ancient spa town of Le Boulou, are included in a week-long walking holiday over the August bank holiday organised by Headwater Holidays (01606 48699). You have to drive to the region, but ferry fares are included in the price of pounds 515.
France-bound families can still get budget accommodation at the height of the peak season. EuroVillages (01606 734400) has availability starting on the next three Saturdays at Les Issambres on the French Riviera. Two adults and up to four children will pay a total of pounds 1,419, including apartment accommodation and ferry crossings.