The changes follow Bauer Media's promotion of Graham Bryce, formerly the regional managing director, Bauer Media Scotland, to the role of group managing director, Place, England and Scotland.
Ellington, previously the regional managing director of the North-East, has taken the role of group commercial director, Place, Northern England and Scotland. She will have responsibility for all local commercial revenues across the Place portfolio.
Steve King, who was the regional managing director for the North West, will take on the role of business development director, Bauer Radio. He will look to develop Bauer Media stations' relationship with listeners through events and new projects.
Bauer Media divided its portfolio into Place, stations such as Liverpool's Radio City that have a strong connection to a local area, and Passion, stations that focus on a particular genre or passion such as Kiss, in 2011.
In her new role, Ellington will report to Bryce, while King will report to Bryce on Place projects and Steve Parkinson, managing director, London at Bauer Radio, on Passion projects.
Dee Ford, the group managing director, radio, Bauer Media, said: "Cath Ellington has achieved considerable recent success in revitalising Metro Radio, increasing audiences and revenues and brings an outstanding track record, fantastic commercial acumen and a wealth of experience to this new role.
"Steve King is one of Bauer's most experienced and successful leaders and his drive, ambition and ideas for new revenue growth which underpinned the enviable performance at our stations in the North West will now be used to great effect across our whole radio portfolio.
"I have never been more confident that Place is in great hands."
Eastwood will leave Bauer Media at the end of October.
Ford said: "I'd like to thank Tracy very much for her unswerving passion, energy and leadership over the last 16 years. She has been a fantastic ambassador for Bauer. We wish her very well for the future."Follow @MaisieMcCabe