EV isn't for everyone obviously, but for that one trip a year, would you not be better off flying, probably cheaper, and saves you time?
Tesla reckons on 1500chf saving per year based on 10-12000km per year - I tend to do less. Additionally my other "big trips" tend to 3 hour drives - say 300km - which is on the cusp of the Tesla's range (over mountains) - and would add a stop.

As I said, I would be keen to try the trip in an EV to see whether it could work - and whether I could adapt/plan the trip to minimise the EV's current CONs.
Give or take (assuming no Ferry strikes) I budget:
175chf ferry
125chf tolls
350chf fuel
650chf TOTALThe ferry price can rise (if we overnight from Dieppe). If we fly our dog has to stay in Switzerland - at a cost of 25chf per day. Flights are around the 300chf mark, on to which hire-car costs have to be added (not like for like) and fuel costs to/from the airport. Driving saves around 500chf (for 2 people).
Plug that back into the Tesla saving (as a cost) and you get 1,500chf/10*8 = 1,200chf - 500chf = 700chf a year.
At present the purchase cost of a Tesla is considerably more (per month) than that of the Alpina.