Best option for replacing car

Hoping for some help here please as am having great difficulty in figuring this out>

Currently drive an A4 with high mileage on it. Looking to change to a newer car.

One option I have looked at is leasing from Audi. Unfortunately it is only new cars they will quote for so figure for a new a4 is €1000 per month for the next 4 years inclusive of tax, maintainence, tyres. (based on 50,000km per annum - travel about 750km per week to and from work - maybe around 250km per week in business travel). Work may be open to this option once it does not cost them money. By this I mean new contract to possibly accommodate a scenario where I forgo a certain figure each year to contribute towards this (benefit here being €10k gross worth of salary/bonuses costs the company €11k inclusive of employers PRSI - what I would really forgo would be €4.8k nett). A fuel card would also cost the company approx. €3k so these would also have to be covered (insurance would be negligible so haven't included for sake of simplicity).
I currently get approx. €6k in mileage expenses each year. With a fuel card this would no longer be incurred by the company.
So in this scenario, the €15k cost to the company (€12k lease & €3k fuel) would be met by 6k in mileage expenses forgone and €9k less gross salary/bonus cost to company.
I would also incur a monthly BIK of 520 under this arrangement. Am I missing something here in thinking the net cost to me would be 920 per month - 520 BIK and 400 net in nett salary forgone monthly?? For this I would get a fully expensed a4 and not have to worry about anything else car related.
Obviously there is a very good chance this would not be allowed as auditors would need to be consulted first as everything would need to be compliant.

Other option I have looked at is to by a 2012-2013 for around €28k. Would trade in current car (worth approx. €8k). Use approx. €10k of savings and take out a loan of €10k costing around €250 a month over 4 years to service. In this scenario, I am back claiming mileage etc but I have to fund tax, insurance, maintenance, tyres and fuel for my own pocket (all after tax income unfortunately!). Obviously in this sceanario, I own the car at the end of the 4 years but given the mileage I would put up. it will depreciate by around 16k I reckon. If I do this, I reckon the car is costing me:
€350 per month in depreciation, €300 per month in fuel, €50 per month to cover tax and insurance, €100 per month to cover maint & tyres, €40 for interest on loan. So that's about €850 per month before work related mileage is deducted (say €400). So car would cost €450 per month - almost half of the cost of option 1 above?

In scenario 1, I do not fund anything upfront and am left with my own car to do as i see fit. Also i am not using any of my savings.
In scenario 2, I will upfront fund €18k so there is an opportunity cost here that must be considered.
Am I missing something when looking at these two scenarios the way I am?

The fuel card will attract BIK tax. AFAIK If you drive 150k business and 50k personal in a year, then 25% of the fuel card usage will be considered a taxable benefit. I'm pretty sure commuting to/from your primary place of work is considered personal use.

When you part ways with this company, under scenario 2 you have still got a car.

If this proposition is really to be revenue neutral, you will be buying somebody's time to administer this scheme. As you are discovering, there's a lot to it: tens of hours per year if your situation is unique and nobody is familiar with this stuff.

Thanks Trasneoir.
I may well be mistaken, but I thought that the fuel card would have been considered part of paying the 30% BIK. The 30% BIK is being used as I am only including business mileage when working out BIK %. Maybe those more familiar could clarify.
In terms of administering the scheme, it wouldn't be hugely complex. Monthly lease figure is set - the only variable is fuel card spend. Would only be a matter of estimating based on historical mileage done and at the end of the year a balancing figure paid.

Valid point on car ownership and the fact I would be entering a 4 yr lease with Audi. The company would be left with it if I decided to up and leave as it would obviously be in their name .
Another point I failed to mention above is losing all of my claims free insured years if I go with the lease option. I have been told I would have to go on company insurance and if I left, I would essentially be treated as a novice driver by the insurance companies.