Boulogne Maritime also had a once weekly in summer charter train for the Italian Tourist Agency CIT, conveying UK passengers who did not want to fly on package holidays with the 'Citalia' holiday company..
This train conveyed sleeping cars only, and I think ran as far as Rome. It was still running in the late 1980's and my (now) wife travelled on it several times to holiday in Stresa, Alassio, Viareggio and Sorrento with transfer by coach from key interchange points to the resorts, from Rome for Sorrento and I'd guess (not the sort of detail she will remember 30 plus years on) somewhere like Allessandria for Alassio and Stresa - the train took the 'direct' route via Modane.
The train ran north from Italy on Friday night and south on the Saturday night meaning a 14 night holiday included one night each way on the train and 12 nights in the resort.
I have just found this link.
As a child I traveled on the CIT train most years from 1975-1983 for holidays in various Adriatic resorts (usually Senigallia).
Luggage had to be loaded on the boat train at Victoria, and living in Tonbridge this meant starting the holiday in the wrong direction by heading to London. Six hours after setting off we would be back in Tonbridge again as the boat train thundered through to Dover!
The first couple of years involved changing at Milan onto a domestic service, but after that the train ran through to Rimini, usually via the Simplon tunnel and Domodossola, but occasionally via Modane and Turin.
I remember coaches in the livery of CIWL - one or two restaurant cars, 2 or 3 sleepers and the rest made up of grey FS couchette carriages (as a family of 4, we had the couchette - sleepers compartments had a maximum of 3). My brother and I used to lean out the windows until I realised the occasional spots of water probably weren't rain! Meals were served in two sittings - very civilised affairs with table cloths, and food which I'm always reminded of when I get my pasta recipes just right.
I've tried to find photos of the train of that era to replicate the exact compositions - all I can find are links like the one you posted (which was after I used it, when it had become all sleeper and no couchettes).
Travelling in late-August / early September also meant usually missing the first week of the new school year (never did me any harm, lol!), French rail strikes (one time our train was joined to another due to lack of drivers for an impressive 23 coaches!), sitting at Amiens for ages waiting for a loco change, and the roughest channel crossings ever!
Flying may be quicker (and it wasn't cheaper back then, hence the train), but you just don't get that feeling of having been anywhere!