Cheapest independent secondary schools in London?

[SaturdaySunday]

Can anyone point me in the direction of "most affordable" independent schools in London for my DS entering Y11? I'm only finding schools that are around £20k but figure there's got to be other options?

Many thanks!

Maybe look at Regent College in Rayners Lane in N W London. they do 1 year GCSE courses

The thread is 8.5 years old. Suggestions now are going to be way too late for a now- 24 year old.