All of the schools the OP listed are Catholic schools ... so assuming you're just including those in your list then I think that St Mary's Ascot is probably the best academically - although Woldingham (not on your list) is probably of a similar if not higher ranking. Given that neither Downside, Worth or Stonyhurst (and why no mention of Ampleforth?) are *that* academically selective, they are unlikely to be in the very top league of schools in the UK