How do I sit an A level privately?

I am in year 12 (meant to be in year 13) and I had to Re sit the year and pick different A levels as AS (I’m doing A2 subjects as well) and I still want to apply to university this year which my school said I can do but I would only have 2 A levels instead of 3 to apply to uni with and Because of this i would have to apply for a foundation year and ask the uni if I can do it with only 2 A2 levels as I would be getting higher grades than what they require. I feel like this would be incredibly difficult and they might not let me (I am calling them tomorrow to check) so I was thinking I could sit A2 Criminology privately as i am doing AS Criminology currently and this would bring me to 3 A levels now which I can just apply to uni with as a first year. I am wondering if i could sit A2 criminology privately and where i would hand in the coursework as that is one part of the qualification along with just one exam.