Just home after 4 days trying to get out.
Here's what we learned:
British Airways has priority - get on one of their flights if you can. Long haul flights seem to have priority over short haul.
Take a flight to any US city and work your way home from there. We ended up coming to NYC via Dallas - connected there to LGA. We paid hefty, but there were at least 30-40 empty seats on our plane - we thought this a real shame since we were sure many other cancelled NYC passengers would have opted for this route over not getting home.
Websites were a better source of info than call sites.
If you can't find out info from your airline, check out the Heathrow arrivals/departures section on their site; this seemed pretty reliable: http://www.heathrowairport.com/
If you are serious about getting home before xmas and you are financially able, you may have to buy a new ticket and deal with the refund/credit on the old one later.
If you are lucky enough to get on a flight, get there early. We were lucky to not have to check, but a fellow passenger told us he waited 3 hours for baggage drop. The good news is, once you're air side, the terminals seem very normal - it's the land side that looks like a refugee zone.
Good luck to all over there - I sympathize with all of you from experience!! Remember that the staff are frustrated too - many of the crew flying out in the next few days will not be able to make it home for Christmas.
I hope this post helps some people.