I have an interesting one for you.
In the eighties, I did a few seasons as a coach driver for a company called NAT Holidays, based in Holbeck, Leeds. NAT officially stood for North African Travel but they were also unofficially known as Never Again Travel.
Their bread and butter work was to provide coach package holidays down to the beaches in the South of France, Italy, Spain and Yugoslavia, using double decker Neoplan Skyliner coaches. However, in 1987, they also used a train down to the sun for a couple of seasons.
They hired couchette and seating rolling stock from SNCF which included a disco/bar coach, and the train ran from Calais Maritime to Agde in the South of France where coaches were waiting to transfer the clients to French resorts. Then the train continued to Perpignan where more coaches waited to transfer clients to Spanish resorts.
As I was on the coach side of things, I never saw this train but I heard it had an SNCF conductor and SNCF bar staff for the disco bar, but the couchettes and seating coaches were staffed by British NAT couriers, working out of the couchette pantries and serving food and drink to the compartments and seats.
The train did not run into Gare du Nord but used the avoiding lines to join the route to the South, with loco and SNCF crew swaps taking place in the Paris suburbs and probably Lyon I would imagine.
NAT had a big set up on Dover docks where we did the coach interchange, and they had a portakabin for the office and catering supplies. A van would go onto the ferry filled with catering supplies which would service the train in Calais.
The passengers for the train would come down to Dover on board coaches from the various pick up points around the UK and then go onto the ferry as foot passengers. All the luggage would be loaded onto BRUTE style luggage trollies and be taken onto the boat. The luggage would then be waiting for the passengers on the platform at Calais Maritime.
The train operated on Fridays and Mondays and only ran for two years, before NAT became part of the International Leisure Group, was renamed Coach Europe, and the train was dropped I believe.
I enclose photos of the 1989 brochure with details of the train. I still have my old NAT Holidays jacket too.