She spent the previous five years at Access UK, where she held various roles, including customer services manager, staff relationship manager, HR manager and group HR manager, before being appointed head of HR in 2010.
She has also held an HR role at Sainsbury’s.
Sims said: “I will be concentrating on transitioning HR at Bull from a traditional back-office personnel function to a business partnering and enabling model.
“This will involve enhancing our people development and employee performance to support the commercial performance of the company, while giving staff the tools, the confidence and the sense of engagement that will help us deliver future success.”