I was in the same position about a year ago. I came to accept that doing A-Levels as an adult is essentially impossible unless you're able to pay thousands and/or move halfway around the country. In the end I did access and I don't regret it. There are drawbacks for sure, but you can always tailor your independent study time for the course you want to pursue at university.
I'm on the first year of a Biochemistry degree currently and I feel prepared. The modules are reasonably challenging but not overwhelming. I seem to be doing well on formative assessments, and still find time to study things not directly related to my course.
Access really is your best option. If Edinburgh is really the only well regarded university you could attend - if you're limited to a certain geographical area for example - only then should you consider distance learning to meet their requirements, but I don't think it will deliver the best educational outcomes for you as a student.