You’re best to ring the tax people and even they might not know but from the debacle that I’ve been through with my company car…
The rate you get paid in mileage when the company are giving you a car allowance will probably be less than the 45/25. Some companies still pay 45/25 but mine only pays half that as they are paying you for the car in the first place.
If you have a company fuel card and access to it for personal fuel that you pay back it’s very hard to justify to the tax people that you are not eligible to be taxed on that fuel.
For example they still taxed me for a company car that was sitting on my drive despite me not being insured to use it for personal use and having a supporting letter from my company to that affect. They justified it with ‘You could potentially use the vehicle for private gains as it is stored on your property’.