Hey, I'm in a sort of similar situation (except with A-levels and personal issues).
I may be wrong but I think if you were to sit A-levels at age 18, your first year would be funded but not the second. I say this because there are people at my sixth form who have had to resit a year and their third year has been government funded.
What is it about the exams that has been stressing you out? I.e. the school environment, fear of failing, pressure to succeed, lack of motivation but still having high expectations etc?
If it's the school environment, then you might want to consider doing A-levels via an online distance learning course. These can be quite expensive (around £400 per subject) but good if you are more of an independant learner.
If it's one of the other reasons, or perhaps a completely different reason, then I strongly suggest focusing on your mental health before going onto A-levels. Of course, it is possible to do well in A-levels if you have poor mental health but if exams worsen your stress and panic attacks to an extreme level, they are not worth it. It is the norm in our society to start A-levels at age 16, go to university when we are 18, but you do not have to follow this path if you are not ready. There are people who work in a supermarket until they are 25 and then choose to do A-levels, and that's fine!
I wish you the best of luck for your gcses and recommend that you focus on those for now instead of the prospect of A-levels. Also, if you are doing quite a lot of subjects, it might be helpful to drop some. At the end of the day, the minimum amount of gcses you need is 5.