Coalesce Function Returning Duplicates
Thanks Martin, using your example answer I have it working using the following code:

SELECT CN.CompanyNoticeHeading, CN.CompanyNoticeText, IsHR, IsApprover, IsEmployee, 
    Locations = STUFF
    (
        (
            SELECT ', ' + LocationName FROM dbo.Locations 
            WHERE LocationID IN 
                (SELECT LocationID FROM dbo.CompanyNoticesLocations WHERE CompanyNoticeID = CN.CompanyNoticeID) 
            FOR XML PATH ('')
        ),1,1,''
    )
    FROM dbo.CompanyNotices AS CN
    INNER JOIN dbo.CompanyNoticesLocations AS CNL ON CN.CompanyNoticeID = CNL.CompanyNoticeID
    INNER JOIN dbo.Locations AS L ON CNL.LocationID = L.LocationID
    WHERE CN.CompanyID = @CompanyID
    GROUP BY CN.CompanyNoticeID, CN.CompanyNoticeHeading, CN.CompanyNoticeText, IsHR, IsApprover, IsEmployee