My desktop research suggests Tesla chargers are only for Tesla owners. There is a trial going on where other vehicles can use them but the trial applies to rapid DC chargers, and these are not compatible with the NX. I believe you also need a Tesla account.
Some companies, like BP Pulse and Shell, charge a lot for their chargers, 50p/kW in some cases. Having a subscription account can reduce those costs but at 50p/kW, the electricity is as expensive as petrol on a per mile basis. Of course, charging at home is a lot less, even taking recent price rises into account. Many other public chargers are around 28-30p/kW. The advantage of the BP and Shell EV stations seems to be that their chargers work, whereas many others do not.
In Scotland, many chargers have been supported under the Charge Place Scotland network and, until recently, many of these provided free electricity. However, Councils have found reliability of the chargers is not as high as expected and have, therefore, introduced (or are about to introduce) charges so that they have the income necessary to keep the chargers operating.
Charging policies vary and are changing as local authorities learn about this brave new world. Some of these policies really don't suit the NX. For example, they have a 45 minutes time limit before a penalty is applied; enough juice for about 10-12 miles of electric only motoring. Others have a fixed fee per session, £3.80 around my way. Good value if charging a full EV from empty but very poor value for topping up a small battery (as are fitted to PHEV)