Generally you can transfer your RN to a leasing company. Dunno if that will work for Salary Sacrifice, but I don't see why not
Price is hyped (compared to just buying a company car)
Insurance, recovery etc. is typically built-in - may be at a rate that you could find better elsewhere
No deposit - good&bad - you can sell your existing 2nd hand ... but you get no ability to reduce monthly amount
Impact on pension (your taxable / pension-able pay is lower)
Your employer might not give you back the Employer NI
If you think the residuals will be good you will lose out on that (no ability to buy the car out-of-lease at the end AFAIK)
But in many/most? cases SS will be worthwhile, particularly for higher tax payers