New job, own car, fuel card and BIK??

I've recently taken up a new sales based role with a UK based company.
My business involves travel from customer to customer using my own car. The company pays an allowance which is taxable. They also provide a fuel card which i can use for private and business mileage. The UK employee's use a mileage management system where they input their travel miles as well as private mileage, and it then calculates the tax due for payroll. Apparently this situation doesnt exist for Ireland and we have to put in a claim at the end of the year with revenue. It is very wooley to say the least.

Has anyone been in this situation before and what records did they keep? how did they claim mileage, and how to claim for business fuel using the fuel card

A car allowance is taxed like pay,but mileage rates up to civil service levels are tax free.Could you not persuade your UK based employer of the benefits to you their employee,of getting reimbursed this way?