We aren't quite as quick of the mark as you, but we used to stop in Ouistreham (Caen port) for a meal on Monday night, after a hard days shopping, and catch the 11 pm boat. We then discovered it was cheaper to stay in a hotel compared to the cost of a cabin/peak rate for crossing. Going back Monday night meant work on tuesday was difficult, so you might as well have the day off.
Hotel rooms range from about £25 a night for the local stuff to about £55 for the Mercure.
You then catch the 9 am ferry on Tuesday
We have done this sometimes, Ouisteham get's pretty quiet after the last boat heads out, which is probably no bad thing. Going on the monday 4.00pm boat this year tho.
However, to answer Philip's original question, this year we're heading up to Deauville on the coast for a top night out in the casino followed by a trip to an exclusive night club till about 5.00am. It's a fantastic drivers road through Lisieux. You'd need to book a hotel. Loads of great seafood restaurants too. Done it before, great fun, but make sure you're not on an early ferry the next day! It's easy to get to either Caen or Le Havre from Deauville too.
