In old money that's around _1.10 per litre, but you will find wide variation, especially near borders. Diesel is about the same in northern Belgium but very much cheaper in Luxembourg, so you will find that reflected in southern Belgium and the surrounding parts of France. Similarly it is a tad cheaper in Spain, so it is also gets cheaper as you approach the border. I paid as low as _0.97 earlier this year on this basis.
As for travel to France, weigh up the cost of fuel from Calais to, say, Angers against the greater cost and longer journed time of using the Caen ferry. As for the short crossings, whilst Dover-Calais is the quickest it can also be one of the noisiest (screaming kids etc) and very congested. Although it involves about 30 miles more (free) motorway travel look at Norfolk Line to Dunkirk - a longer crossing but usually much more comfortable.
Finally, look at www.autoroutes.fr - it helps if you now a little French. It will calculate a route for you that takes you on or avoids motorways, and also (and most especially) takes account of whether you are towing a 'van or not. Autoroutes in France are very smooth, quick, and good to drive but will cost you 6c/km solo or 10c/km towing. You can pay with a credit card. Take care not to exceed the relative speed limits (they change when the road is wet) as your distance is timed.
Facebook
Twitter