This was just a quick long weekend away to get another ski trip in, and wasn't sure I was going to write it up. Then I did a search, and saw that there haven't been many trip reports, and certainly nothing in recent times on what it is like to travel by what is quite a unique method of travel - loading your car on a train, and riding that under the sea. So my trip report on driving from London to the French Alps via the Eurotunnel.

Eurotunnel Booking and Pre-departure
A group of friends was going to be down in Les Houches, which is a ski resort in the Chamonix Valley on the main motorway between France and Italy through the Mont Blanc tunnel. Myself and another friend, plus a friend of hers weren't able to get away for a full week, but a long weekend was possible. We found an AirBnB (one we had stayed at before) without issue, but flights to Geneva were proving expensive, and so we decided to drive down on Wednesday night to be on the slopes Thursday morning.
People may think that driving 10 or 11 hours through the night to ski the next day is a daft thing to do, and you may be right. But I've done it before, and it isn't as bad as you think it will be, especially if you can split the driving. And when it comes to costs, you have to pay fuel, tolls and the Eurotunnel booking, but offset that against the flights, extra baggage fees for the ski equipment, and having to book a car anyway to transfer from the airport up to the slopes, it can be more cost effective.
And so we booked in on the Eurotunnel, and reserved the AirBnB.

For booking a Eurotunnel crossing (also known by their new branding "Le Shuttle"), you choose a date and time to cross, and enter the details about the vehicle you are taking. There are different classes of tickets, depending on the length of your trip, type of vehicle, whether you want the trip refundable, and whether you want to have the flexibility to turn up at any time, or lock into a specific crossing time (more on the actual flexibility on this later). For our trip from a Wednesday to a Sunday, we got a Short Stay Saver fare.
To book a fare, you need to enter the number of passengers and the details of the vehicle you are taking (vehicle type, number plate, type of fuel).
Initially we planned to head down in my friend's car. However, it is a rather long in the tooth Audi A3 which was having some reliability issues. As her car was both shaky on if it would actually make the trip, and also awfully small for 3 people and their ski gear, we made a pivot and I ended up renting a car from Enterprise. Luckily, you can easily change the details of your booking with no fees, assuming you aren't changing the class of vehicle you are taking.
Prior to your trip, you do need to fill out an API (advanced passenger information) for each passenger. When making your booking, you need to specify the number of travellers. This includes name, gender, date of birth, nationality, and passport details for each passenger. This can be entered any time after your booking, and doesn't need to be entered all at once, so each member of our party went in and filled in their details individually. You can add, remove and change traveller details any time up to entering the Eurotunnel site.
Though it was only a week and a half ago from when I travelled to today, already the Covid travel requirements have changed for both France and the UK. So at the time, for the trip down I need to provide a vaccination pass and a "sworn undertaking to comply with the rules" form. This could be done anytime from 4 days prior to your departure time.
Car Rental from Enterprise, Hammersmith - March 9, 2022
As previously stated, we decided to rent a car to go down. I booked from one of my local rental agencies - a branch of Enterprise. I have rented from them multiple times, and have always found them very reliable and excellent.
To take a rental vehicle out of the UK, you need to pay to have the paperwork that says the owner of the vehicle (in this case, Enterprise) allowing you to take it out of the country. In addition, you pay additional for EU roadside coverage. As we were also splitting the driving, we paid another £15.60 a day for the additional drivers. In all, the rental and all the extra gubbins cost us £558.18 (though I was able to get some discounts for what was about to happen).
As we had ski gear, I rented a "Nissan Qashqai or similar." Everything was all set when I got a call at 10AM on the 9th of March, 2 hours before I was meant to pick up the car. Seems the car they had planned to give me had been returned with mechanical issues. Would I be happy to pick up the car at 4PM instead of noon?
As our crossing was at 5:20PM in Folkestone, there was no way to pick up the car that late and make it our train crossing, so I said we couldn't. The agent said she would call me back.
It was a tense 20 minutes while I waited for a call back, and I went through various permutations and combinations of what we might do (take my friend's car anyway? rent from another agency? change our departure time?).
Enterprise called back and had found a solution. And so I was able to show up at midday and pick up a Hyundai Kona, a hybrid small SUV.

The car was alright, but felt a bit small to me as compared to a Qashqai. I also found rubbish in the car from the last rental. I mentioned my disappointment at those items, but as it was the only suitable car available, I took it. Enterprise refunded me £59.30 (15% off the base rental price) as a goodwill gesture.
This was the first time I have had issues with this branch of Enterprise, and they seemed very keen to try and make things right for me, so I'd still recommend them if you ever need to rent a car in Hammersmith, London (your only other option is Sixt, which is always priced much higher than Enterprise).
And so I went home, loaded up the car, picked up the two passengers and loaded and reloaded the car a couple of times, and away we went.