I knew I was taking a chance, booking a car ferry to France at short notice when the cabins were gone. But if you live, uh, dangerously, what you miss with the early bird you gain with spontaneity. After booking, I checked the cabins online several times a day, and within a week a cabin cancellation for the outward journey popped up. Bingo. I was so confident for the return leg. A long boring journey that’s bearable with your own tiny space and a reasonable bed sounds like a bit of an ordeal without them. I knew it would work out. Someone was bound to change their plans and change their booking. I didn’t factor in ferry-time France in mid August, and a lack of sufficient cabins onboard for a full ship in the first place.

Come boarding time for the return trip, after a terrific and varied traipse around France en famille, and still no cabin; not even a Pullman seat. Surely it can’t be that bad. And soberly, get a grip; there are so many enduring life and death sea crossings not so far away.

Roughing it’s not a problem: we’ve travelled comfortless in far more adventurous spots (though not paying Ireland-France ferry prices through the nose for the pleasure). Bring some blankets and provisions and we’ll be grand. Mind you, 17 hours is not far shy of 24 – how do you while away almost a full day and night: two adults and their 11 year old, trapped on a floating cafeteria with hundreds of strangers and no privacy on a softly rolling floor?

We belt onboard like warriors, but the queues for the purser’s desk to register for cabin cancelations are so long we abandon immediately and fan out to find a suitable spot. As does everyone else. A banquette seat beside the children’s play area in the café seems a good bet. The seat’s not big but it’s one of the few cushioned ones; there are a few TVs, but none too close. We hitch up a couple of bucket chairs, close the nearby window curtains to keep out the light in the morning, and spread our blankets, nesting instincts surfacing. It’s not 8.30pm yet and we haven’t even set off.

The boat’s full. There are families, groups of friends, a gang of teenage scouts, and three sisters and a single priest or monk sitting chatting, all in long cream robes, like a surreal vision of a past pious world.

The area next to us is nabbed by three strapping young men with tattoos, one of whom sets off to get a pitcher of beer.

Nearly midnight The café and children's play area are still pretty lively, but we are not. I persuade my Small Man to nestle down on the floor and try to sleep with the light blazing and the crowds madding, and amazingly, after an hour or two, he does. Grown Man eventually snoozes in what looks like a position that will result in back pain tomorrow.

One of the Tattooed Trio has rolled out a sleeping bag on the floor, stripped to his under-beneaths and got into the bag to sleep. The remaining Tattooed Two have no intention of similar, and launch into another pitcher. They sit companionably and silently, surfing in mobile phone isolation, working their way through the beer.

1:30am Mine are asleep (Small Man) and decently dozing (Grown Man) but I'm still awake. The café lights are still on fullbeam but most all left in the café are attempting to sleep. I watch as a couple of the scouts in toggles and woggles sit down and chat . . . and flirt perhaps. This will be a memorable passage of night and rite of passage for them. Every so often people wander around looking intently at those sprawled and messy, gaping mouths and cricked necks. Are they looking to pinch sleeping travellers' gear, or for a comfy spot to camp? (The latter.) As soon as the children's small soft play area next to us is vacated, a woman with two children spy it and colonise it. Right next to us. Dozy or what? We really were not on the ball; next time I'll know where to head for. Tattooed Two fetch another pitcher.

Bored and tired and uncomfortable and nosy, I get up for a ramble. All is peaceful. There are no rowdies holding up the bar shouting and singing shanties. It’s impressive how well prepared some people are for a cabin-less night. One family has installed two large airbeds plus duvets in a tiny lobby between two doors making a fantastic, comfy nest. Further down toward the bar and restaurant the lights are dimmer. People are stretched out all over the place in sleeping bags. One person has a very fancy and impressive full-height campbed, and is safely in bo-bo-land, surrounded by sleeping bag city. Where are the retro nuns and priest, who were sitting near here earlier? Are they well kitted out in the camping department or disorganised like most on board? Are they still in the magnificent robes, now rumpled and grubby, with a crick in their necks from sleeping at an angle?

Back at our nest, I ask a staff member (they’re all lovely, they’re neither French or Irish) can he turn the lighting down, please. Unfortunately, they don’t have control over the lighting in this area, and, inexplicably on a boat so poorly supplied with cabins, the lighting must stay at full throttle through the night, as the passengers attempt to sleep. Not much need to have drawn those curtains then.

4:30am I look over at the Tattooed Trio. Several empty pitchers on the small table. TT number one still slumbers in the bag on the floor, and the other two are now also asleep, awkwardly on the banquette seat, spooned into each other like lovers.

Small Man is still asleep in his nest on the floor; Grown Man is awake and has moved over to the nearest TV where he watches a complete Mel Gibson action film in the middle of the night. Eventually I nod, in and out of partial consciousness, slightly aware of what’s happening around.

Morning Action gradually starts around 7am. Only another five hours to go. Thank God for toothpaste, and a book. Minions is on in the tiny pay-for cinema at 9am; highlight of the morning.

Yes, it’s been bearable, an experience, not a big deal. Though it feels like a bit of cheek to charge premium prices for a grotty journey. The holiday ends in Cherbourg. On the way off the boat you can tell the unlucky uncabined ones by their bleary eyes, and the pillows tucked under the arms. Nearly home. We’ll sleep tonight.