Hi, I think the applicability of my response will largely depend on the course that you want to do next year - I'm assuming something medical related due to your subject choices. If you're not doing something medical related, or your unis have not specified that you need to pass the practical endorsements, then you won't need them. Personally, I've applied for Psychology at uni - starting Sept 2025 - and do not need to pass my biological practical endorsement (I've missed a large portion of the practicals due to ill health) so not all courses do require you to pass them. I'm also unsure which exam boards require course work for biology/ chemistry? Unless I've read that wrong.
Anyway, If you DO need the practical endorsement, there are a lot of exam centres that can provide that service. Unfortunately it is quite expensive - most charge around £750 for practical endorsement per subject, and I don't think that includes the cost of the exams. I'm not sure how much AS levels cost, but most A level subjects cost £250 to sit privately - I personally paid £230 for my three sociology exams that I'm sitting this year as a private candidate. Look at exam centres close to you that offer the practical endorsement and checkout the potential costs - I'm honestly not sure, but some exam centres may reduce the price if taking two... I hope for your sake that they do, but this may not be the case.
I am sorry to hear about your health - I completely understand. I've personally taken 3 years to complete my A levels - sat 1 A level last year, after two years of sixth form, and have taught myself Biology and Sociology this year (am enrolled onto a biology intensive course but haven't attended college much this year due to health). Do take your time with this - there are so many options you have that can still get you where you want to be. Have you looked into access to higher education courses? Or, depending on where you live, some colleges do offer A level intensive courses (I live in London, there's a college in London that does it).
However, if you choose to sit Chemistry/ Biology privately next year, then I would recommend using Uplearn (you can get it for free if you're family earn under a certain income) - I've largely used that to teach myself Biology this year and it has been invaluable so I would really recommend. Not sure how good it is for Chemistry though.