Everything else is included in the price of the vehicle and is standard https://www.tesla.com/models
Under specs they list
* Access to Tesla's expanding Supercharger network
* Mobile connector with 110 volt, 240 volt, and J1772 adapters
* 17" capacitive touchscreen
* Onboard maps and navigation with free updates for 7 years
* Automatic keyless entry
* ...
"If your vehicle is eligible, the Supercharging upgrade option will be visible in the Available Upgrades section."
http://shop.teslamotors.com/products/enable-supercharging
The S40 has the hardware for Supercharging but is excluded by policy.
I'm only aware of this because a friend in the UK has been trying to work-out what's applicable in this market and Tesla's constant changes to the policy makes that difficult.
By no means 'free': there was a $2000 Supercharger access fee included in the purchase price of the S85, or $2500 to enable it after purchase for the S60.
Not available for the S40 variant which wasn't permitted to use the Superchargers.