The Companion to the Standing Orders says "A Grand Committee is a committee of unlimited membership. Any member of the House may participate in it. Only one Grand Committee sits on any one day. The place of meeting is usually the Moses Room." While amendments are discussed in Grand Committee, they are never voted on. A contentious amendment will be withdrawn after debate, to be re-introduced - and voted on - at Report Stage.
This week the Dormant Bank and Building Society Accounts Bill was considered in Grand Committee. The first day can be seen at http://www.parliamentlive.tv/Main/VideoPlayer.aspx?meetingId=633
and day two at http://www.parliamentlive.tv/Main/VideoPlayer.aspx?meetingId=634 . The third day has yet to be fixed.