The potential for depreciation was a powerful deterrent for me. Assuming 20% depreciation a year, then a £65K Tesla would be "costing" over £1000 a month just in depreciation alone.

However, the Tesla Model S has apparently so far had lower depreciation than any other car in the UK[0], according to CAP Black Book ("the industry benchmark for used car values"[1]). Presumably this is in large part due to its relative scarcity (still a 2 month lead time for a new one, so an instantly-available second hand one becomes more attractive). Quite how long that situation holds remains to be seen.

[0] http://evobsession.com/cap-black-book-teslas-retain-value-be...

[1] http://www.cap.co.uk/en/products-and-services/black-book/

EDIT: The 20% depreciation was a rough estimate based on the Resale Value Guarantee if you buy on finance. Using figures of £64,600 cash price, £72,477 if bought on finance, and £37,584 Guaranteed Minimum Future Value after 3 years, then the actual "worst case" depreciation would be around 18% per year over 3 years.