Is the company VAT registered?

The amount to recognize as an asset will be it's cost price (net of VAT if you do VAT)
The contra account for the recognition will be the finance lease agreement, remember that the vehicle is the asset and the finance lease agreement is the liability, no VAT is payable on the liability downpayments (other than maybe the bank charges, if you post it in detail like that)

When you see the payment going out from your bank account against the finance lease/hire purchase (old term) or installment sales agreement, whatever you call it, the bank account will decrease in the credit side (or increase if it's in the red already) and the liability, the finance lease, will decrease in the debit side.

So yeah, the easiest is just to post the payment you do in the cashbook against the loan, you can correct later for the split between what was the capital, interest and bank charges, but normally these would just be like journal entries when you compile reports in like Excel for example, it's also easier to wait for the annual amortization schedule too, but in any event, you can choose to do the adjustments for the split between these if you always get the info reliably and if it's productive or otherwise necessary to do so.