Fuel Card / Tax Relief

Hi,

I am the director of a family-run private limited company and would like some advise on how to handle the dreadful fuel dilemma.

I use my Company Fuel Card to pay for fuel filled in my Personal Car which I use mostly for work (85% of miles are work-related). A fuel card saves me having to collect receiepts. I do not reclaim VAT on fuel as I'm under Flat Rate VAT Scheme.

Do I need to make a log of each work-related journey to act as proof of the 85% of miles are work-related?
What process/method should I use? Is it to pay the company from my wages (after income-tax) for personal miles? (if so, what rates/calculation do I use)
Am I better off paying for fuel using a personal credit card, collect reciepts, then pay myself through the company the work-fuel portion, and then claim the tax relief on the p11d?

I'm alittle unsure of what the best process/method would be - in the sense that, least admin-work required, and tax