What one of our conversation group (who is forever going backwards and forwards to the UK) does is geta a seat then tucks himself behind the luggage area in the lounge where he can stretch out and have a kip!
That crossing is lovely if you have plenty of money and get a cabin as the early departure means you can have a good meal in the restaurant and still gt 8 hours sleep…
Beyond my budget these days though.
When our Club took the ferry to Corsica… those who wanted to sleep booked cabins… albeit sharing … fascinating sharing a cabin with 3 very classy Parisian ladies… and all their frills and dazzle 
I knew them well… before the trip… and even better after the trip… 
OH was in with the boys… and slept well as he couldn’t hear the chap who snored…
I can imagine!
My favourite UK crossing is definitely Cherbourg/Poole because it’s short but the timings are now awful so I rarely use it (Not that I’ve been back for a few years now but you never know…)
My main problem with the St Malo crossing is that it is marketed as a cruise experience and the boats are exactly what you would expect with that kind of label. I prefer simple with no entertainment or beauty salons or anything like that 
I’d look for comfortable seating/sleeping and good food… no need for entertainment etc…
My priorities exactly!
Absolutely, stretched out on the floor (or a couch if you can get one) definitely better than the reclining seat.
But I’m getting a bit old for those games.
My wife & I made a pact years ago - never travel without a cabin. It helps that with our usual travel arrangements we can make use of the free day cabins (if you have a vehicle).
No. Not even in campers. 'Elf n Safety…
I think we’d only do it these days in an emergency.
Observation re security control prior to boarding at Portsmouth.
Vehicles pulled into the control shed were there for some time, 10-15 mins. I saw the bonnet up on several cars - and not a cursory look, several minutes.
Being in the ‘tail-end-Charlies’ line [campers and vans] I saw who got pulled into the shed and who got sent on to the ship. When a vehicle left the shed, the next to come fwd was pulled in. The following vehicles were all sent on until another space came up in the shed.
So it was totally random and pot luck to avoid being pulled into control.
I must just look dodgy then as I seem to get pulled in most trips.
That said the checking has become fairly perfunctory.
Nothing perfunctory about the checks yesterday at St. Malo. 10-15 mins per vehicle. Maybe that’s why the ship sailed < 2 hrs late!
But made up the time at sea.