What I found (and what I think the video shows) is that my car will ask for letters (eg LS) and then one or more numbers (LS17) and IF I enter 2 numbers, it will automatically add a space (EG LS17_) and then ask me to add another number (EG LS17_1) and at the same time, locations in LS17_1 appear to the right of the letter wheel. Then mine just defaults to 'OK' which enables me to click to the menu on the right and choose my rough location. I then polarise that using the street address usually.
NOW though, although the nav defaults to 'OK' as described above, I can just ignore it and scroll round to 'letters' again - allowing me to enter the last two letters (EG LS17_1TB.)
SO, that's why I wasn't sure if I could do that before or not - I jsut never tried until I watched Charlie's video.