Can I go back to a-levels or a BTEC?

Hi guys, this is my first post but I have a question that needs answering;
I’m 20 years old, I dropped out of college two, maybe three, years ago while I was studying A-Levels (media, business, ICT and maths) as I could see myself slowly deteriorating while doing them. I did not make it clear to my college that I was dropping out due to my mental state as I was too embarrassed/in no state to admit there was an issue.

A few years have gone by now and in the time past I’ve set up my own business, conquered my mental health and really turned things around. The thing is my dad is willing to employ me with his business, which will be a very high paying role, on the basis that I go and get myself a business qualification - be it A-Level, BTEC or above. So I’ve decided I want to chase that option, get back to college and maybe even go to university after. I just wanted to know how to get the wheels in motion if it’s even possible? Any help is massively appreciated