A few answers to set the ball rolling - some of these are guesses (?)
1 is the Formula 1 Grand Prix circuit
6 (b) Becket & More Both Thomas, both archbishops of Canterbury, both killed allegedly at the behest of a King called Henry? (II & VIII respectively)
6 (d) Avilla and Lisieux Both Saints called Theresa. The second one known as The Little Flower was in the news here in Ireland last year because relics of her remains were on a tour around the country
7. All US holidays ? Last one is Thanksgiving.
10(a) Scientific Units ? Not sure which ones
11 was a Eurovision song contest but I don't know details requested.
15 Motto ? Be prepared
17 Brian Boru Irish High king died at the Battle of Clontarf (1014) after a Good Friday disagreement with a Dane called Brodir. So he was before William the Conqueror (1066) and Marco Polo (13th Century?) not sure about the others. I know I read a Ladybird book about Hereward the Wake once, but he's not well known in these parts and I can't remember much about it. Don't know dates for the others.