I think they all have internal practical assessments for physics and chemistry. I'd steer clear of OCR Salters - as that contains a large project element for chemistry, which is good but not particularly doable in your situation.
Basically, for the practicals, normal students do them in a class and sit a paper that accompanies it (where you put your results, and answer some questions) under exam conditions. It may be that you can do the exam at a nearby college/school when their students are doing it (and hence, you'd want to be under the same exam board they teach to), but i'm not entirely sure about the way these things come about.
Maths I suspect you can do with whatever - I did it on AQA, 100% exam-based.