The Raithwaite Suite can accommodate 140 theatre-style and has a private entrance and terrace overlooking the gardens and woodland.
The Headlam Suite takes up to 30 theatre-style or 16 in boardroom formation, while the boardroom accommodates eight.
Stokers Lounge can be used for cocktail receptions for up to 120, or informal meetings for up to 20.
Mansell has worked for West Paces, Capella Telluride in Colorado, and Capella Castlemartyr in County Cork.
Skelwith Group managing director Paul Ellis said: "Richard’s appointment signals the start of the final push to the grand opening this October. His experience, which spans across various areas of hotel operations and management, makes him a tremendous asset to our staff and to our guests."
Up to 50 people from lead contractors Wates Construction are currently on site completing the work.