Crossed the channel recently on a saturday night on board a Sea France ferry. I have used them before and never been overly impressed but this was something else. In particular the service in the restaurant was appalling. At 9.30 at night the only dish available was sausage & chips, absoutely nothing else. And for a plate of really poor quality food plus a small glass of very ordinary red wine I paid something around £12. even paying for it was a hassle. Lots of people queuing up with their sausage and chips and just one till open so that by the time you get the food to the table it is stone cold.
The toilets were quite disgusting, overflowing, not flushing, foul smelling, just awful. I complained about this at the information desk and the only way the woman could have been less interested was if she had been asleep.
Take my advice, go by some other company, fly , take Eurostar or if no other choice just swim - it'll be more pleasant than going by Sea France.