I've been meaning to write this since we did this trip in the New Year. I'd been fretting about the trip so much and had been searching the archives here for tips. Well, I'm glad to report that we survived and even enjoyed the trip so I thought I'd share our experience in case anyone is interested.
We spent Christmas in Northern Spain, western side - we went there by ferry, from Plymouth to Santander but that was the last sailing they did until March so we decided to drive back through France and get the boat back from Caen to Portsmouth.
We have 3 kids: 5, 2.10 and 9mo. We set off at about 10am on New Year's Day. The kids just played for a while until we stopped a couple of hours later for a break. We'd borrowed some friends' DVD players and they were a godsend in the end. After the break we plugged them in with a film they hadn't seen before and they were completely quiet for a good hour. The nearly 3yo started moaning a bit after that saying she wanted to get out of the car - I kept her busy until the film finished and then stopped for lunch just before the border with France. They then slept for an hour, played for a bit, stopped for a break, put another DVD on and we got to Saintes - just north of Bordeaux - at 6.40pm. We had booked a Premiere Classe hotel there beforehand. It was easy to find - oh yes, the trip would have been A LOT more stressful if we hadn't had the TomTom with us - it was brilliant throughout and really accurate with the time predictions. The rooms at the Premiere Classe were very basic and tiny (a bit like a boat cabin) but perfectly clean and comfortable and they cost 35 euros for the night. We booked 2 rooms because of there been 5 of us but in the end we all slept together in the same room (we still had to pay for both though). There was a double bed, a single bunk over the double bed where both DDs slept together and then a cot for DS. There was a restaurant next door where we had dinner and breakfast in the morning was very reasonable and the staff really friendly. We set off at 8.30am and we only had a quick toilet break until we stopped for lunch at Alencon. Again, the kids were mostly entertained looking out of the window, playing and the DVD. We had to get off the motorway to stop at Alencon but we loved it as it finally felt we were in France rather than a random motorway in a random country. We stopped for 1.5 hours and fitted a quick lunch and walk in the town. Then it was just 1.5 hours to Caen and the kids slept almost all the way. The boat left at 4pm and we got to Porstmout at 10pm. Then another 1.5 hours to get home and the kids were asleep all the way. There were loads of service areas in France, every 20 minutes or so, where we could have stopped for the kids to have a good runaround and play but it was very very cold (around 0 degrees most of the time) - I can imagine the trip would have been even better in the summer; we could take picnic-style food and eat outside while the kids played in these areas and it would have been even cheaper. The boat from Caen was completely fine and it was worth booking a cabin in the end even though it wasn't an overnight trip. By the time we had a drink, then played in the kids area, had a rest in the cabin and then dinner, the trip was over.
We spent not quite 60 euros in petrol and 65 euros in toll charges.
All in all an enjoyable trip and we'll certainly consider doing it again.
I hope this is useful to someone .