Jessops are flush with 5d2 stock, whereas the D700 is difficult to find, and even WEx had to wait a month for the 15 they ordered. I tried a 5d2 last weekend out of waiting frustration - it's a nice camera, but the body just felt a little too lightweight, and I prefer the onbody control ethos of Nikon to the dual button functions of Canon. Added to that the fact that, for my needs, the AF and low light capability are inarguably better on the nikon and I decided to continue the wait.
For me, the Nikon is worth the premium. If I was a landscaper, I might feel differently!