The film will be the latest adaptation of Julia Donaldson and Axel Scheffler's popular books, following on from the likes of The Gruffalo, Zog And The Flying Doctors and, most recently, Superworm.
Gavin And Stacey star Brydon returns for his 10th production as Uncle Smoo, alongside Strictly Come Dancing champion Bailey, who will play Grandfather Smed.
The voice cast will also feature Bridgerton star Adjoa Andoh as Grandmother Smoo, double Oscar nominee Sally Hawkins as the narrator and comedian Meera Syal as Aunt Smed.
The film will tell a tale about a pair of aliens from two rival groups who fall in love, sparking strong disapproval from their families.
Sex Education star Ashna Rabheru will play Janet while All American actor Daniel Ezra will play Bill, and the pair will lead the cast through a cosmic adventure.
The film is being directed by Daniel Snaddon and Samatha Cutler while Barney Goodland and Martin Pope have been appointed producers.
Donaldson and Scheffler's The Smeds And The Smoos will be on BBC One at Christmas.