I haven't given too much thoughts to resits, but we're lucky in that I know my DD's school supports repeating years and "Y14," although I guess it could depend on circumstances.
I've had a brief Plan B discussion with DD at her initiation. I wasn't going to discuss until after exams, but it came up. We agreed I would book a just-in-case UCAT for her, as she is away on holiday this week (lucky with the weather!) whereas I am stuck at my desk. So I booked a September UCAT on Tuesday. She did surprise me by saying that she can't think of anything worse than going back to school for another year, and would seriously reassess trying to get in to undergraduate medicine if she didn't get her grades. I guess it's a real test of her commitment to medicine!
To be honest, as medicine is still a very academic degree as well as vocational, I would support her decision not to resit unless she came very close to her required grades first time. The teaching at her above-average-but-not-exceptional state school has been a bit wonky, but there haven't been any exceptional circumstances, and if she can't get 3 As now then she'll probably struggle with the demands of the course.
@crispy2019,I would check out the exam boards your child has been studying under before considering online learning. My DD did the less popular OCR boards for all three (and the even rare OCR-B Salters for Chemistry), and it's a lot harder to find support for those boards. I heard great things about Uplearn and offered to pay for it for DD but when she looked at it, it was no good for any of her boards. The OCR syllabuses focus more on skills and applying knowledge, and are (so I understand) less formulaic than AQA and Edexcel. I think it's therefore helpful to have in-person learning here, as you can't just spam questions. Having said that, my DD needs to work things out for herself and so she hasn't sought much support from teaching staff outside of class. So consider learning style too. Is there a local college they could attend instead maybe?