BIK - company car - mobile employee

Hi i have a complicated question relating to BIK. I hope someone can help me with

If an employee has a company car and the employee is mobile looking after a number of shops / units nationwide.

Their journey commences from home and they do not call to company office on route. from where is the commencement of business miles calculated? is it the distance from employee home to destination or is it the distance from the company office to the destination.
My company tells me it is from home as I am not an office based employee. But i cannot find guidance on this on revenue . ie
the only item i can see on this is when a company van is used / the calculation is the lesser distance of home or office to destination. There is no reference if it is a car

If the final journey is directly home and not via office what two points are used to calculate business miles?

if business miles are calculated as the distance from office to destination and vis versa but the journey to the office is notional how does this effect BIK as these personal miles are not actually travelled?

does the 8,000 private miles incorporate the above?

can the rule of reduced rate be applied under the 70% out of office rule if business mileage is 35,000

sorry about the complicated question but Im really confused.
thanks a million