The trip was based around a 2 centre off roading break - see
http://www.dora4x4.com/adv-two-centre.shtml for details.
Tremolat, the home of DORA4X4 is about 8-10 hours from Calais depending on route, day of travel etc.
The 4 offroading days were approx 9.30 to 5.30 with minimal tarmac sections. The Wednesday travelling between the 2 locations took around 5 hours including an hour diversion to see the awesome Millau bridge as featured on Top Gear.
Andrew and Karen are excellent hosts and will sort accomodation (including a delightful cottage of their own if required) to suit, with camping available in the summer.
Costs are dependant on type of accomodation and fuel etc. but I covered close to 2000 miles including the 350 getting to and from Dover in the UK.
Contact Andrew for more details, he is very helpful and will advise you of the options.