It's never too late, you can do A-levels whenever you want
If I were you, I wouldn't bother enrolling into college, instead I'd opt for the "private candidate" option, with this option you can complete AS/A2 in 1 year aswell, so you can actually go to university next year if you're this determined, this is the most flexible option for older students, and AQA, OCR and Edexcel all accept private candidates aswell
But if you aren't too fussed about time, then you could always go for the conventional 2 year college route, but in my opinion I think getting yourself a tutor would be best, not only would it be 1-on-1 teaching so you're more likely to understand concepts with ease, you'd also have more time to work a normal job, so you can save up and pay for all these modules.
So basically, get a tutor, buy some text books, work your ass off, and then book yourself to sit the exams at a local examination centre for external candidates (your local college might even accept you for this), check the AQA, OCR and Edexcel websites for prices of modules
So you can complete your AS modules in January and your A2 modules in June, I know it sounds like a lot of work, but if you're determined it's very possible, not to mention A-Level Chemistry and Maths are straightforward, none of this remembering pointless information and regurgitating it in exams, you learn methods and mechanisms and then you apply them, simple.
Best of luck to you, whatever you decide.