The passenger train doesn’t run, but the Eurotunnel car thing does. It’s hideously awfully expensive though, looking at it - and you need to go with a vehicle as far as I can tell. Can’t advise whether it’s any good, haven’t used it, but details at http://www.eurotunnel.com/uk/home/
Pretty much everything restarts on Boxing Day, but the timetable at www.eurostar.com is showing no trains for 26th/27th December, either - so maybe they’re the exception! I think it’s more likely that they just don’t allow booking this far out via the website, perhaps.
The ferries are off on Christmas Day too, although according to their publicity it’s the only day they don’t schedule.
One thing to think about - if you’re going to Paris for the day, I’d research what’s likely to be open. If you’re going to see something specific, I’d check it doesn’t close Christmas Day - an awful lot of stuff does, in a lot of European countries.
Eh? It looks pretty cheap to me - £71 one way including car and all passengers: Eurotunnel - Le Shuttle... I’ve used it and thought it was great, but then I was going for lunch in Boulogne, not driving to Paris.
But yes, you do need a car, it isn’t for foot passengers. And the OP would still have to get from London to Folkestone.
Christmas Day is basically a write-off for the vast majority of public transport options. It’s the one day of the year when pretty much every business and transport option shuts down. Only hotels and a few restaurants serving Christmas lunch are open. Even the Tube is down. If I was you, I would book a lovely lunch in a good hotel or restaurant, brace yourself for the cost, enjoy walking around an empty London, then, if the Eurostar is still down, book a cheap flight to Paris.
Actually, that’s a thought, airports don’t close and Christmas Day tickets are often cheap. You could fly London-Paris – which airport is best will depend on where you’re coming from.
Is this a day-trip or a transfer to continue your holiday in France? It might dictate our replies.