Whilst there are a number of direct freight ferry routes to Spain, the most popular way to get to Spain for vans is usually to just travel on the Dover to Calais route then drive through France. This is because it's normally the most cost and time effective way for couriers to get to Spain.
As van drivers are not tied to tachographs they are able to get across France much quicker than drivers of rigid or articulated vehicles (and whom are subject to driving restrictions).
DFDS sail 10 times a day from Dover to Calais, taking around 90 minutes. For those in even more of a hurry, Folkestone to Calais on Eurotunnel is also a popular option. These crossings are all open tickets making them great for flexible requirements.
For artics and rigids to get to Spain the best and most popular routes are usually the direct ones. Taking you from the south coast of England into Northern Spain is Brittany Ferries from Portsmouth to Santander or Bilbao. Direct freight ferries to Spain normally take around 24 hours allowing for a long rest period on board.
Of course, there are also great onboard facilities such as cabins, restaurants and bars allowing for a complete journey in relaxation rather than driving on the roads. Ferries to Spain normally sail around 3 or 4 times a week.
Other ferry options for travelling to Spain is to get a ferry from England to Brittany, and drive through the west of France into Northern Spain. These are good options if you do not wish to sail all the way to Spain, but still want a good overnight rest, and access to on board facilities such as a cabin etc. Examples of such routes, great for all types of freight vehicles (vans, lorries, and artics), are Portsmouth to St Malo and Portsmouth to Caen.
Both of these services are operated by Brittany Ferries and take between 6 and 11 hours depending on how calm the seas are.