I think that every British actor appeared in the movies! I saw an interview with Bill Nighy who said that when he was asked to play Rufus Scrimgeor he was relieved as he felt he was the only actor left in Britain who wasn't in a Harry Potter movie.
Bill Nighy - David Talbot...more dreaming. See: Best Exotic Marigold Hotel, Harry Potter Deathly Hallows (pt 1), Underworld, Pirate of the Caribbean: World's End, Hot Fuzz, Shaun of the Dead, Constant Gardener, Love Actually. Hitchikers Guide to the Galaxy, Being Human
20 BEST CAST#01 ϟ Harry Potter (Daniel Radcliffe, Emma Watson, Rupert Grint, Tom Felton, Evanna Lynch, Bonnie Wright, Matthew Lewis, Helena Bonham Carter, Ralph Fiennes, Jason Isaacs, Alan Rickman, Maggie Grace, Bill Nighy, Gary Oldman, David Thewlis, James & Oliver Phelps, Robbie Coltrane, Michael Gambon) NOTHING IN THE WORLD IS ENOUGH TO EXPRESS HOW MUCH I LOVE THEM.