I'd like to buy a reproduction of a painting by Franz Marc, I know the
painting has a picture of a white dog sitting down (I think looking
away from the viewer).  I need the name of the painting so I can get
the reproduction made.
I know it's not "Dog lying in snow", though I think it is the same dog
as in the picture I'm looking for.
Bonus points for finding a company who can supply a oil on canvas
orginal size reproduction to me in the UK (before Xmas)

Dear Chuffy, 

The name of the painting is "Der Hund vor der Welt" (The Dog before
the World), it has been painted in 1912. The painting is stored today
in a private collection. It is 111 x 83 cm.

See: 
Beruehmte Hunde - Franz Marc 
http://www.beruehmte-hunde.info/kunst/bildende_kunst/bk_img/franz_marc.jpg

I could find two online stores selling it - both are American and
shipping to the UK. However, I am not so sure about "original sizes";
and personally, I cannot also vouch that the painting will be at your
doorstep before Christmas:

Art Studio.com 
<http://www.arts-studio.com/cgi-bin/shop/shop.pl?fid=1104661536&cgifunction=form>
- shipping to the UK for free. The closest size to the original is 108
x 81.6 cm.

Angel Art House 
<http://www.angel-art-house.com/ProductDetails.aspx?ID=4478> -
shipping to the UK for free. The closest size to the original is 40x30
inches.

I hope this answers your question. Please contact me if you need any
clarification on this answer before you rate it. My search terms:
[franz marc 1912 dog]
[Franz Marc]
And of course, the name of the painting.

That's the puppy!  Thanks very much for a speedy result.

Thank you for the rating and the tip!