Doing an A Level outside school/college

[Levithian]

I'm looking at doing an A Level at the same time as my son, and we both want to do the same course (Philosophy.) He is only doing 3 A Levels as his college doesn't offer Philosophy (which he wants to study at uni) and so has the time/support to do the work at home.
Has anyone done anything like this? I'm thinking that I can buy course aids/material (I've looked at the curriculum and past papers on AQA website) and we could study ourselves, and then book into an exam when we feel ready. But how realistic is this? Is it really something we could do ourselves? (There is a financial aspect to this... I've seen courses that cost £800+ not counting the cost of the exams, and it's money I just don't have atm.)
Any tips or shared experience would be appreciated!

Dd did but she had assistance from school. Her school didn't offer philosophy but her GCSE RS teacher offered to help her. She actually ended up doing RS but a particular syllabus/exam board that was heavy on the philosophy content. A nearby high school offered this syllabus and one of their teachers offered to mentor dd's teacher as she had never taught A level before.

So basically dd bought the textbook and worked through the content and had a weekly hour long tutorial with the RS teacher in a free period. The teacher set essays and sent some of them off to the other high school for a 2nd opinion.

She got A*

Thank you Comefromaway, that's very helpful. An A* is very impressive! DS did a philosophy OpenLearn course in lockdown and is very interested, but I'm struggling with the practicalities of exams etc.