i can't remember the price of unleaded 98 at auchan but it's worth a look (it's on the junction with the centre commercial signposted somewhere around grand synthe). the diesel is around 10 cents a litre cheaper than on the autoroute at mannekensvere just over the border (the texaco on both sides).
for ferries, don't use those cost saving sites, and don't use seafrance. unless coachtrips with thousands of children and people who... smell a bit odd and ferries you can't catch a sleep on are your cup of tea! they're also completely inflexible unless you shell out more for their flexible ticket. norfolkline and p&o both allow you to catch the earlier or later crossing for no amendment fees. that's more of an advantage for the longer drives, especially norfolkline who do crossings every 2 hours. it means you have a 4 hour window for traffic and organisational fails rather than 2 at the most. plus if the crossing you want is say, £20 and the one before or after is £10 you can book the cheaper one and get on the expensive one free of charge
