The last of the Channel ferry brochures are arriving on the agents' shelves about now, so motoring skiers are finally able to make informed comparisons between the costs of alternative routes. To get you started, here is an overview. The following figures relate to return journeys.

For most skiers there are two main alternatives: a quick crossing from Dover or Folkestone to Calais or Boulogne; or a longer one to Normandy or Holland, preferably undertaken at night.

I'm a fan of the latter approach, which for most residents of southern England means you can leave home in the evening and be on the autoroute or autobahn bright and early the next morning, and can reach, without strain, a wide range of resorts within the day.

There are two main groups of useful routes. For those based west of London aiming for the western Alps, the obvious crossings to consider are Portsmouth to Le Havre (P&O) and Portsmouth to Caen (Brittany Ferries), then on French motorways via Paris to Geneva, Chambery or Grenoble. For those based further east heading for the Swiss or Austrian Alps via the German motorways, the main long-crossing alternatives are Harwich to Hook of Holland (Stena Sealink) and Sheerness to Vlissingen (Olau).

If you don't fall into one of these two categories, the equations become more complicated: you will want to weigh up the journey to the embarkation port, the distance from disembarkation to resort, the timings and relative costs.

Both companies operating the western routes offer two basic kinds of fare: component ones, in which you add up the fare for your car and for each passenger, and inclusive fares, which cover the car and up to five people. Both are lower if you return within 10 days.

Two adults travelling together will find Brittany Ferries' inclusive fares cheaper than their component ones, but will find the converse with P&O. There is little to choose between the two companies, although Brittany Ferries has the edge. Assuming you travel overnight, a total fare of about pounds 185 will buy a two-berth cabin with washbasin from P&O, but a cabin with shower from Brittany Ferries. If you're going for more than 10 days, you'll pay about pounds 215 for the same facilities.

Not surprisingly, inclusive fares look even more attractive to a larger group sharing a car. A family of four occupying a Brittany Ferries cabin with shower pays pounds 226 for 10 days, pounds 256 for longer. P&O's inclusive fares become more economical than their component fares for a group of four, but work out quite a bit higher than Brittany Ferries if you opt for a shower.

On the eastern routes, the operators offer a similar choice of component and inclusive fares, but with an additional complication: Olau's inclusive fares vary

according to when you travel, Friday and Saturday nights being appreciably more expensive.

Overall, fares on eastern routes are considerably higher than those on the western ones. Two adults sharing a cabin comes to pounds 272 with Olau, pounds 336 with Stena Sealink; for a family of four, inclusive fares become attractive, totalling pounds 338 with Olau (if you avoid weekend travel), pounds 376 with Stena Sealink. The fact that German motorways are free (whereas tolls in France mount up) doesn't fully compensate for these higher fares.

On the shorter crossings from Dover and Folkestone, you have three possible modes of travel: conventional ferries operating from Dover by Stena Sealink and P&O; Hoverspeed's hovercraft from Dover; and, rather confusingly, Hoverspeed's catamaran (or SeaCat) from Folkestone.

Price comparisons here are normally simplified by the irrelevance of cabins. The cheapest is the last: the 50-minute journey by SeaCat costs pounds 112 for two, pounds 121 for a family of four or five. In contrast, the 35-minute hovercraft is the most expensive at pounds 138 for two, pounds 150 for the family.

Conventional ferries take 75 to 90 minutes to cross the Channel and, near as dammit, cost the same: pounds 125 for two (component fare), pounds 135 for the family (inclusive fare). Single adults planning to take two children should note that they can save a few pounds with Stena Sealink (which charges pounds 10 per child) rather than P&O (which charges the full pounds 25).

Sally Ferries' Ramsgate to Dunkirk service strikes me as an unhappy compromise: at 2 1/2 hours, it is too long to appeal in the daytime and too short to be satisfactory overnight. Not surprisingly, there is compensation in the fares, which are similar to SeaCat's: pounds 115 for two, pounds 122 for a family.

Sally, Stena Sealink and P&O all offer special ski deals, packaging ferry fares with continental motor insurance and other benefits - and adding another layer of complexity to these already intricate cost comparisons.

P&O's Ski Fare and Stena Sealink's Ski-Link provide winter sports insurance. For two, they are identically priced at pounds 159; for more, Ski-Link becomes appreciably more expensive. Sally's package provides snow chains but not winter sports insurance and costs pounds 139 for five. The Sally and Stena packages are slightly more expensive at peak times.

Whether you can make the best of these packages will depend on your circumstances. Finally, if you're tempted by the insurance- based ones, don't forget to check the terms of the policy.