The answer to this depends upon whether you use simplified expenses or not. If so, then the rates are also 45p for the first 10,000 miles, and 25p for any over this. Simplified expenses can be used by sole traders and business partnerships that don’t involve a limited company. If you’ve already claimed capital allowance for the car in question, then you wouldn’t be able to use simplified expenses.
If you’re unable to use them or choose not to, then they’ll need to be calculated differently. This will affect how you claim on it. As you’re self-employed, you wouldn’t take MAPs into account, but claim the entirety of your business mileage as tax relief on your Self Assessment tax return.