You don't half to "cash it through a company" to claim 100% WDA in the 1st year.
You can still purchase on finance/PCP and claim full WDA if you wish.
You can still claim 100% WDA if you are self employed.
You might not want to claim the full 100% anyway as you have to give the WDA saving back...
Yes they are over a 2/3 year lease. Although I am buying and not leasing I added on the Performance Battery Plus as the Residual Value Predictions show that the the bigger battery will be worth more on resale, for at least the 1st 3 years of the cars life, than its extra cost at new.