Anyone flown pet(s) from Heathrow to O'Hare?

We're moving back to the US right before Christmas (ugh) and I'm just upside down trying to get everything sorted. We're using PetAir UK and flying on BA - I'm a bit nervous about flying into Chicago on Dec 22 (I am expecting it will be cold) and haven't found anything about flying there in the cold (I found restrictions for flying in during July).

Has anyone flown their pet BA into O'Hare? I'm still waiting to hear the pickup process, but I'd appreciate hearing a first-hand experience.

NOt sure how helpful this may be to you but at least its a response for now--

We flew our 2 dogs from Manchester to Ohare about 3 or 4 years ago.  I can't remember who we took but it was a direct flight on an american carrier (I'm thinking AA but not sure).  Anyway at the time we flew them as excess baggage so did everything ourselves.  We took them to the check in desk inside the airport with the rest of our stuff.  After we checked in we took them with us through security so their kennels could get checked and then they were taken from there with an agent for boarding.   

In O'hare we went through immigration as usual and then at baggage claim got a porter with a large flatbed to collect our luggage first then he took us to the very end of the area where the odd sized stuff like skies and stuff waits for you.  There was a door that he went to and from there collected both our kennels.  Then we followed him to the far other side of the area (flatbed and someone who knew what they were doing was very helpful with all this)  to a small room/ area that was the USDA.  I had all my paperwork, fit to fly letter, rabis certs etc ready to show and the agent literally just asked what flight we were on and said "OK, thanks" and let us go.  From there we went to the customs agent that you pass right before you are out the door and gave our form and that was it.  Went out to meet our ride.

I'm not sure if using an agent would be different and you'd then go collect them from the cargo areas instead.  As far as the weather- everything we've been told (flown dogs 3 times) was it had to be over something like 10F at time of take off and landing- I think.  The airline should be able to tell you the numbers.

As far as paperwork nobody looked at anything I had. I was told the just needed a current rabis cert and the airline wanted a fit to fly letter but I was never asked to show either to anyone.