Definitely in judging the required range based on what I have seen regards possible charging points. Plus that annoying fact that unlike fuel pumps if all the spots are taken they could be taken for a long time.How often do you get up to and around Scotland? That's one of the key things. Unless or until batteries take a huge step forward, a 500 mile honest range would just mean be a huge, heavy and inefficient EV - carting all that weight around for the occasional long trip
The charging infrastructure is the weak point as we all know I'm sure. If that can be sorted then there's no reason why the majority of people would need more than 200-300 mile honest range. Toilet break and a leg stretch and/or some food and ready to go again.
PHEV's get some hate but I think if the use case fits then they're a good choice at this time. Some of them can do 40-50 miles on the battery now.
Once that's sorted I'd definitely be willing to stop a few times for 30 mine or so.