Narrowed down my new car choices to either an E-Class estate or a T5 type thing (both used, budget £10-15k)

I then got wondering if I did go the route of a van could it be a company vehicle (Ltd company engineering consultancy/R&D mix and a van would be useful at times).

I understand I will have tax to pay on the BIK (tax rate x £3,150), BIK on personal fuel use (tax rate x £594) and NI (13.8% x £3744). So certainly not free use.

I currently use a bangernomics estate and claim the mileage allowance on that (15k business miles) but am wondering hot it all works with my paying for fuel as a company. Do I just claim the exact fuel use and running costs (tax insurance etc) or does the company use the 45/25p rate? I did read that I could also pay for the fuel myself and thus avoid the BIK on fuel and then claim the 45/25p but that seemed odd if the company owns the car unless I am paying for the servicing and insurance myself and not the company.

Personal use is about 5k a year, business use 15k.