Here's a link to the pdf version of the latest manual although it is, as you have noticed, one manual for all versions of the Corsa:
Corsa- manual July 2020
Your car's mileage is shown in the lower-left corner of the binnacle. Your remaining range is a work of fiction that is shown in the lower right of the binnacle. It is usually referred to as the GoM (Guess-o-Meter). It will try and guess the remaining range based on several factors including your recent driving style together with such things as the outside air temperature, air conditioning setting and other things. There are 2 trip computers you can use, accessed by the rotating knob on the left-hand stalk.
Also, if you have the 10" infotainment screen, you can see the cars cumulative efficiency in the graph for each journey. This is probably a better indicator of the range you have if you use a little bit of maths. The battery is 50kW (approx 47kW usable) and it is easy enough to calculate your total range from 100% charge. For example, if your efficiency is showing 4.0 miles/kWh, then your approximate range is 4.0 x 50 = 200 miles. The efficiency will vary depending on many factors including how heavy footed you are and the temperature, weather etc.
Also, you have a horizontal bar graph of the battery sectioned into 8 segments from 0% to 100% SoC (State of Charge). Each segment is 12.5% of charge. If you want to be extra safe and cautious, you can plan on each segment represents 20 miles of range. So, if you have 2 bars remaining, you have at least 40 miles of range left and you may want to consider recharging at this stage.
Apart from when the battery is above 95% SoC, the car will regen whether in D or B mode. It's just much less in D mode.