Have never used the Eurotunnel.
Have a preference for the ferry.
Prefer the Dunkerque-Dover crossing, that ferry 2hours, is more comfortable, less noisy than the Calais crossing.
Once drove to Calais and they had not cleared the snow.
If you get late night /early morning crossing, then the roads to London are clear. You should get to W. London in about 2hrs
Remember to keep some water in the car, as good for keeping you awake. If any passengers, then wet wipes (baby wipes) handy to freshen up as you go along.
Remember to keep some small euro coins for the WC on route
If we have the time we tend to make sure we have petrol before the ferry, as a pain having to search when one lands. If you do land at Dover and need Petrol ask the boarder control where to go, as we once almost ran out in our search

At Reims I have stayed on a few occasions at the Novotel .. it is outside Reims (the other side of Reims), just a stone's throw from the motorway junction. Good price, perfectly adequate rooms and restaurant is ok too. From there it is 2 hours to the Eurotunnel terminal.

I always do an over-nighter trip, leaving Basel at 10pm for the 6am-ish crossing from Calais/Dunkerque. There are the odd overnight roadworks (down to a single lane in parts), but never any traffic. I have a wee 118d so no need to refuel (~4.7 litre/100km) i.e. Basel to NW London on a single tank

Luxembourg def worth it for Diesel (and since the prices are set by the government, motorway stations are as expensive (or cheap) as off-motorway ones). Just avoid rush hours around Luxembourg (7:30-9 in the morning, 4:30-6:30 pm).

About half what I'll use in the new car

Last time I did Dieppe - Newhaven to the UK - because I was meeting with friends in Brighton on the Saturday - worked incredibly well.

One the way back I did Portsmouth - Le Havre - and spent the day cruising through France enjoying the journey.

We have in the past left Zurich around 4pm - and been able to do it in one night (to London). My best time for the journey (Tunnel-Zurich) is 6hr15mins - but I estimate 8hrs for the trip.