Ali, I agree that 3A* places one in a terrific position that obviates the number of GCSE’s taken.
However, most 3A* students were also star pupils in Year 11 and took more than the 5 basic GCSE’s.
But here, OP DOES NOT have 3A*'s. It looks like he has B’s (based on what he wrote) at school
and is not preparing ALevels.
I don’t know any public comprehensive, free, or independent school that only offers 6-8 gcse subjects although that may very well be the case - except, again, that OP doesn’t attend one of these schools.
OP said he attended a Sabis school and while s/he didn’t provide a link, I looked it up, and these are private/independent schools in many countries, with excellent academic offerings - they even request students take some GCSE’s during Year 10 so that they can focus on more advanced GCSE’s in Year 11.
Directing OP to fairtest is a good idea. Here’s a list of top-tiers that don’t require the SAT (although they may require SAT Subject tests).