hey dude,
assuming that you're in the Johannesburg area, go chat to a gentlemen by the name of Riaad from BMW finance in Midrand. He will be able to assist you in Financing a private second hander for a fee that BMW charges. I can see why your dad's bitching about BMW finance as they are amazing at their rates as well as their after sales service. Keep your business in-house and you'll be fine
Good Luck