Thanks so much for all the replies. Journey was pretty good!
In the end, we planned carefully and included 6 stops using ABRP. I checked each stop in Plugshare, and built the route in Google Maps. Weather was perfect- mostly dry but cool, no air-con needed. Each stop was about 20 minutes. With two kids in the back we arrived feeling better than we would have if we’d bombed it down the whole way in a petrol car. ABRP and PlugShare worked well. Biggest issues: too many electric cars trying to charge! At Route 303 cafe (amazing views) and Exeter RaceCourse (four EVs appeared for one charger). It’s also not always obvious how many cars can charge from a single charger point. Some places it’s one, others its two. They need a universal symbol for this I think.
The way back ABRP said 5 charges only, which worked fine. A couple of them needed slower speeds (52mph and 61mph), but this was fine as they were on fairly slow roads anyway.
Luckily the weather wasn’t too hot on either trip, so we didn’t desperately need air-con. I would recommend anyone who wants to do a trip like this to give it a go if they’re not under time pressure. It was a lot more straightforward than I expected.
Stats in case useful to anyone else considering this kind of trip:
My Nissan guessometer usually says 82 miles when fully charged. I set ABRP to an extra 30kg weight (it was much more than this in reality), 90% SoC at start, reference consumption 3.03 MI/KWH. Used ChaDeMo chargers throughout, 15% charger arrival SoC, Max SoC = 100%, 5min charging overhead, and allowed it to adjust speeds
I'd be interested if anyone has used ZapMap and compared it to ABRP for a journey like this. Looks like a nicer interface, but less detailed calculations?