Re: A levels from london ?
if you looking for top notch private independent schools in London or Around.
try
Eaton
Harrow
above two are like Atchison of UK and i guess are full boarding schools and expect highest fees too. But also note, many prime ministers and presidents around the world have attended above schools.
now if want to look for schools in London, state schools/colleges are free of cost for locals, I havent seen any one advertising for international students.
private and independent schools do accept international students as they are not funded by govt. almost all the colleges offer A level and above vocational education. hope it helps
by the way why you want to do A level in London, when you can do this exam from Pakistan as well. it will have same weight.
I would suggest you should go for a degree in UK after finishing you A levels in Pakistan. That will be good.