Well, Coopers and Nottingham are really completely different. You will still end up with beer, but it'll be different. Not
bad different, just different.
Coopers is much more estery than Nottingham, imparting more fruity flavors and aromas when fermented at the same temperatures as Nottingham. Nottingham is widely admired because it ferments very "clean"; that is to say, it does
not impart much in the way of esters.
If it were my beer, I'd choose a fresh packet of Coopers over buying two vials of White Labs yeast of any type - because that's what you'd
have to do, if you wanted a properly vigourous ferment and didn't want to make a starter. "Pitchable vial", my angry white male backside.
Let's look at it this way - Edwort's HPA can have some fruity esters in it. Pale Ales of any type, an estery profile is appropriate. So Coopers is a viable choice. Now, if you were brewing Edwort's Belgian Pale Ale (not that he's listed one; I'm just sayin'), Coopers yeast would be inappropriate, because it won't provide the right flavor/aroma profile. You dig?
Cheers,
Bob