My normal drive is 70 miles a day and the Tesla is ideal. For the longer journey (about one a fortnight) I’ll be in a less efficient (mpg wise) ICE but expect to save about 5 hours of my own time.
Getting home at 9pm as opposed to 2am makes a massive difference
That is some kind of inventive thinking there. It will not take you 5 hours more
Here is a trip from Southampton to Scotland in 5 C with an SR+
A Better Routeplanner
That's 1 hour 15 min at superchargers. Nowhere near the 5 hours you are imagining. In an ICE you would definitely stop at least once, unless you can go 7 hours without a pee break and your car can do 580 miles on one tank in the winter. Here you are stopping 6 times for ~15 min every hour or so.
Change that to the LR and you are looking at 3 stops every ~2 hours and a time saving of ~30 min.
So you definitely wont be seeing a 5 hour difference between ICE and ~300 mile range EV, especially a Tesla. 1-2 hours, sure, not 5.