Thank you so much epontius & Darby for pointing me in the right direction. Knowing that I needed to motion track using corner pins meant I was able to do further searching and I found some tutorials & guides (see yikesmikes' recent post for a list of tutes & guides:
http://forums.creativecow.net/cgi-bin/new_read_thread.cgi?forumid=2&postid=... Sadly, through my reading and experimenting in AE, I've discovered that I had probably broken every rule during the shoot (actors block the corners of the painting, the camera tilted down so that some of the painting was off screen at times etc) and so am unable to motion track sucessfully throughout the entire shot. Well, at least the painting was well lit!
Steve Nevard's recent post
http://forums.creativecow.net/cgi-bin/new_read_thread.cgi?forumid=2&postid=... is one of several that showed I am not alone in encountering these issues in post. He ended up using a 3D Tracker (Monet).
As an "emerging" freelance editor, I can't quite quite afford this software, so I am devising a workaround where I will zoom in to focus on the actors until they move away from the painting (excluding the painting from the shot), when I can do a successful corner track as the frame is wide then with all 4 corners unobscured. There will be a few seconds where part of the painting's frame is in shot as the actors get up - I may be able to use a lens blur to place the background out of focus at this point.
Thanks once again for your advice - all other suggestions gratefully received!
