Figs look good on first glance,You're looking at the dividends on the purchase price. In the "no depreciation example", in year 1, assuming 100% FYA, you'd save 28k on the dividends, assuming you pay yourself out in full, but when the car goes, the CT is 2-3k higher and you'd have 54,990 in the company to pay yourself so you'd pay 28k more, and possibly even more than that if rates go up, in the year the car goes. The net is you are worse off.
The dividend "saving" is effectively against the depreciation and runnng costs for tyres, insurance etc, over the life span of the car, not the purchase price.
An example using very rough figures (please somebody comment if I'm wrong)
Year 1 (first colum is not company car, second column is, car is 100k and 50k for easy figures.
100k - 100k profit
0 - 50k FYA allowance
100k - 50k net profit
18k - 9k corp tax
82k - 41k dividend
28k - 18k dividend tax (need to check my rates are right)
Year 2
100k - 100k profit
0 - 0 FYA
100 - 100 net profit etc
Year 3 sell car
100k - 100k profit
0 - 40k from selling car
100k - 140k net profit after car sale
18k - 26k corp tax
82k - 114k dividend
28k - 40k dividend tax
I did spreadsheets for all of this when working out the various options, but also have a half decent accountant who highlighted some other marginal savings.