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AIUI, the rollout of superchargers in the UK has been impaired by difficulties in getting wayleaves for electrical supplies, at several proposed supercharger sites.
As regards insurance, if you shop around and perhaps try using an insurance broker familiar with LHD cars from Europe, European insurance, etc. , you should be able to have your Norwegian or other European years of No Claims history recognised for your UK No Claims Bonus.
Several UK insurers are not really familiar with EVs or Tesla and will quote huge premiums. Direct Line has an arrangement with Tesla UK - don't use their normal car insurance site, use their Tesla specific page. LV and Novo are also familiar with Tesla cars.