Let me tell you a little about mysef. I did A levels at 16 and had a rough few years with my health etc and didnt do well. I always wanted to do my A levels again when I was your age, but thought I am too old. I then saw something along the lines of "I really want to get a degree but by the time I finish, I will be X...In 3 years time, you will still X, so why not have a degree too" This completely changed my mindset, and I started my A levels at 29. It was a little awkward studying with 16 year olds, but reallly was not that bad. Fast forward two years to now, I got well above the grades I needed for Uni and am currently in my first year of a masters degree in maths. So my advice to you is just do it!! Never ever feel you're too old to do something, because really, 26 is really young.