Looking at the gridlock on M20 yet again ,you will be lucky getting to France anytime soon if travelling down sarf
Portsmouth - Caen ... no problems
And much nicer area around there than Calais. Only downside is its a 5hr crossing.
Not sure if they still do the vomit comet crossings to Caen / Cherbourg, but they were significantly quicker.. if you have a strong constitution! Otherwise, leave in the evening, book a cabin, couple of beers on the boat and breakfast in a little Cafe in France.
Nah .. leave home at lunch time down to Portsmouth to sail mid afternoon, sit in the sun on the boat and watch the world go by ... nice entrecote bleu for dinner around 6 with a glass of red .. then a pint in the bar, dock around 9.30, 10 minute drive to the site, legs down crack a few beers. Up around 8.30 in the morning, leisurely breakfast, legs up and tow for 5 hours down to the Vendee (including a stop for lunch) getting on site around 3.30 pm ... awning up, crack a beer and start the barbie around 6.00 pm .....