A bit of an update on this.
I haven't had the opportunity to use the van much as I have been waiting for an appointment for the body builder to fit all of the lining and racking. I did however have a good drive up to them to deliver the van yesterday. Here are my initial thoughts and findings.
I plugged in with the battery at 98% around 2 hours before leaving and used the (dreadful) MyCitroen app to start the 45 minute pre-programmed/21°C heating cycle. I noticed that the charger contactor didn't engage to start the charge. Clearly the van will not 'top-up' when near full or to help with pre-conditioning/climate.
The predicted range displayed on leaving was 181 miles. The temperature was 1°C and the climate set to a moderate 19°C with AC off. The first 10 miles were a mix of town and B roads, all quiet and done in the Normal drive mode with regen on. Efficiency on the display stated as 2.2miles/kWh for this part of the journey. The predicted range depleted in accordance with the miles traveled. All good.
This soon came undone however with the last 40 miles of motorway driving. Cruise set at 70mph. I got to my destination with a total journey distance of 52 miles with 55% battery remaining and a predicted range remaining of 64 miles. Efficiency for the motorway part of the journey was 1.7miles/kWh.
Bear in mind that my van is the 75kWh version and is the XLWB variant so it is heavy and is likely not as efficient as the smaller 50kWh SWB version. Even so, and in consideration of the temperature, I was still surprised by the result. I guess time will tell and we'll see what it is like to live with. I have yet to try it fully loaded (which it will be most of the time)

. Thankfully I am realistic about the range. I reckon 100 miles fully loaded at this time of year. That's ok with me. The efficiency does bother me though. 2.2miles/kWh is quite poor but no doubt this will get better with warmer weather.