Below £20k PA. Best Value Fee Paying/Independent Schools In Hertfordshire and Bucks?

[Delectable]

The title says it all really. Which schools charge below £20k per annum in the Hertfordshire and Buckinghamshire areas and produce good results please?

I just learnt of Stowe School at £15k but not sure how well it performs.

I'm interested in those in the top 100 GCSE and A Level league tables please.

Thank you.

@parboil yes I'm aware there're horrid privates just there're horrid non fee paying schools.