Phillip Jeffries Astoria Floral.

http://www.phillipjeffries.com/products/5105--voyage_collection.html

To the trade only, unfortunately. You'll have to contact a designer to buy it for you.

The one above is close, but not quite the one.

The one pictured seems to use more naturalistic line drawings; at least, that is what it looks like on my monitor. I could have sworn I saw this wallpaper (in two versions: this one, and one with a black ground) on Coronation Street last week...

This paper by Schumacher has a similar feel in that it has lovely line drawings (although it is black and off-white, has colour, and branches instead of flowers):

http://www.fschumacher.com/search/ProductDetail.aspx?sku=2704420

(will keep an eye out for th done in your picture... looks like a Scandinavian source?)

OH YES!! Stunning and hope you find and enjoy!

Not identical, but with a similar feeling, Farrow and Ball in a grey colorway.

http://us.farrow-ball.com/the-ringwold-papers-bp-1604/ringwold//fcp-product/201604

Similar paper available from The Home Depot:

http://www.homedepot.ca/product/205-in-w-beige-grey-linear-leaf-flower-trail-wallpaper/905383

Unfortunately it doesn't seem to come in a colour that is predominantly grey.

Very similar:
http://www.mptapeter.dk/leverandoerer/eijffinger/bisou/tapet_eijffinger_bisou_310022.htm

check out Graham & Brown's Premier Collection. They have similar patterns and they're Paste the Wall so they're easy to hang/remove.

Is this Graham & Brown Juliet wallpaper it?