Good question. We use cable which is 18mm in diameter (think garden hose and you won’t be far off) and this cable needs to run from your Consumer Unit or sometimes your meter cupboard to the charger. We normally find that it is neatest if the cable is routed outside as quickly as possible in order to minimise the amount of cable that can be seen inside the house. Once outside the cable is clipped every 30cm, normally along the base of the external wall, until it reaches the charger. For some installs we can route the cable so that it goes straight in the back of the charger with no external cabling visible.
If your property has a cellar or a suspended floor then it is often possible to route the cable this way to minimise the amount of cable on show. Some of the trickier installs are where extensions have been built and the consumer unit has not been moved – this means that the consumer unit is a long way from the nearest external wall and, in the absence of a suitable void in the floor, the cable has to be routed internally.