They will begin performances June 16 at the Queen's Theatre, also newly joined by Celinde Schoenmaker as Fantine, Michael Colbourne as Enjolras and Emilie Fleming as Cosette.
Rob Houchen will continue to star as Marius, Carrie Hope Fletcher as Eponine and Wendy Ferguson as Madame Thénardier.
Lockyer has also appeared as Chris in Miss Saigon on Broadway and in the first national tour and as Marius in the 10th anniversary production of Les Misérables on Broadway.
Saxton has previously appeared in Les Misérables as Enjolras and has also been seen as Raoul in Love Never Dies. He won the 2011 Olivier Award for for Best Actor in a Musical for his performance as Giorgio in Passion at the Donmar Warehouse.
Schoenmaker returns to the role of Fantine at the Queen’s Theatre after making her West End debut in the part in 2013. She most recently played Jenny in Love Story on tour in Holland.
Colbourne, who makes his West End debut as Enjolras, most recently played Young Buddy in a concert version of Follies at Guildford's Yvonne Arnaud Theatre.
Fleming was a finalist in BBC1’s "Over the Rainbow." Her credits include Oliver! at the Crucible Theatre, Sheffield. She also took part in the Les Misérables 20th Anniversary performance schools finale at the Queen’s Theatre.
The full company from June 16 will also include Jeremy Batt, Ethan Bradshaw, Melanie Bright, Dougie Carter, Jade Davies, Lee Dillon-Stuart, Tamsin Dowsett, Christian Edwards, James Gant, Carolina Gregory, Bradley Jaden, Emma Kingston, Sarah Lark, Jordan Lee Davies, Adam Linstead, Joanna Loxton, Claire Parrish, Adam Pearce, Jonny Purchase, Michael Riseley, Simon Shorten, Ashley Stillburn, Jessamy Stoddart and Helen Walsh.
To book tickets, which are currently on sale through April 25, 2015, contact the box office on 0844 482 5160, or visit www.lesmis.com