Incumbent James Bowling has decided to step down to pursue other oppurtunities.
Dilks has been finance director at Regatta Group since 2016. He joined in 2009 as financial controller of its Craghoppers brand.
Before this he held finance roles at Kraft Foods and The Co-Operative Group.
Dilks will join Sosandar on 7 September and Bowling will remain in his role until 18 September.
Ali Hall and Julie Lavington, Sosandar’s joint CEOs, said: “Notwithstanding the current environment, the opportunity for Sosandar is significant. With [Stephen’s] experience across brands and markets, Stephen is well placed to work alongside us to deliver continued growth and shareholder value going forward.”