I reckon a foundation degree in art and design, or a foundation year that continues on to a degree course (takes it from 3 years to 4 years of study) is the way to go! Also going back to college to complete an art course could be an option!
If you've painted and drawn since school, you can probably build an amazing portfolio of work, and then the foundation degree/year will give you the not sure what to call them, but like doing things like working to an assignment, doing artist research and analysing work and whatnot. (This is going off of stuff I did at college for a Level 3 Extended Diploma in Art and Design, also I'm a bit tired due to a cold atm so I can't confidently say I'm making sense😆).
Personally I'm looking at a local university that offers a four year course that starts with a foundation year in art and design and then leads you to start the 3 year degree in a specific course such as fine art, or animation or photography. But someone has suggested a foundation degree in art and design, which could be studied at a college or university (i think, depends on if its offered or not?).
But yeah, overall I say just go for it! Try contacting a local uni or a uni you like the idea of going to (doesn't have to be a firm choice) and see if they have any advice to offer as well! Hopefully some uni reps will reply to you on here as I've seen them do on other posts cause they're super helpful and can give you some more info too😊