Dench, 86, took first place on the female list, scooping the title ahead of Oscar-winning The Favourite star Colman thanks to her role as M in the James Bond franchise and starring performances in movies such as The Best Exotic Marigold Hotel, Philomena and Iris – and despite playing Old Deuteronomy in resounding flop Cats.
Hardy – known for starring roles in Mad Max: Fury Road and The Revenant – pipped Connery to the title of best British male film star of this century just six months after the latter's death last October aged 90.
Connery retired from acting in 2003 after starring in mega-flop The League Of Extraordinary Gentlemen.
Sir Anthony Hopkins, 83, who is hotly tipped to win his second Oscar this year for The Father, came in third in the male category.
Downton Abbey and Harry Potter star Dame Maggie Smith came in third in the female category, followed by Dame Helen Mirren, who won multiple awards for The Queen, at fourth and Kate Winslet, who won her third Bafta for Steve Jobs in 2016, at fifth.
Film fans were also asked to name their Best British Film of the 21st Century, with the Harry Potter franchise coming out on top.
Smith was not the only Potter actor to make the film star lists: Emma Watson and Helena Bonham-Carter also came in at sixth and seventh on the female list and Gary Oldman at ninth on the male list.
Romantic comedy Bridget Jones' Diary, starring Renee Zellweger, Colin Firth and Hugh Grant, was voted second on the best British film list and French revolution musical Les Miserables, directed by British filmmaker Tom Hooper, came in at number three.
Bridget Jones stars Colin Firth and Hugh Grant both made the male film star list, at fourth and 10th place respectively.
James Bond star Daniel Craig was voted the fifth best British male film star.
Family favourite Paddington was named the fourth best British film, just behind Christopher Nolan's war movie Dunkirk.
Other actors to make the list included Sir Ian McKellen, Dame Julie Walters, Liam Neeson, Keira Knightley, Benedict Cumberbatch and Emily Blunt.
Other films in the Top 10 varied from stop-motion animation Wallace And Gromit: The Curse Of The Were-Rabbit to Danny Boyle's post-apocalyptic horror movie 28 Days Later and Shane Meadows' coming-of-age drama This Is England.
Mark Barlow, UK general manager for Showcase Cinemas, said: “Our study to celebrate the very best of British just goes to show how much talent there is amongst our filmmakers and actors.
“It’s great to see Dame Judi Dench taking the top spot as she really is a British icon, and the full list of the favourite films since the turn of the millennium contains some unforgettable titles.
“As we reopen our cinemas next month, we have even more British films to look forward to this year, including Peter Rabbit 2, The Father and of course Bond is back in No Time To Die.”
Watch: Charlize Theron has Tom Hardy self-portrait
The Top 10 Male British Film Stars of the 21st Century
Sir Sean Connery
Sir Anthony Hopkins
Sir Ian McKellen
The Top 10 Female British Film Stars of the 21st Century
Dame Judi Dench
Dame Maggie Smith
Dame Helen Mirren
Dame Julie Walters
The Top 10 British Films of the 21st Century
Harry Potter series
Bridget Jones’s Diary
The Theory Of Everything
28 Days Later
Wallace And Gromit: The Curse Of The Were-Rabbit
This Is England
Watch: The top 5 James Bond movies, voted by experts