Actually, I've been looking into the same thing, because I'm currently finishing up my pre-college courses and was planning to apply to schools in the UK. But according to the local british council office, subjects that require course work, laboratory work, and continious assessments are not available for independant applicants, I don't know exactly what the A level physics ciriculum looks like but I'd bet there's some course?lab work in there
A levels does look great on an application, but it's not for everyone I'm afraid. SATI and SATII are reasonable substitutes though, and easy enough to get. Even top unis like oxford accept them.
Do check in with the british council at your country if you can work something out.
best of luck :-)