Hops substitution

I'm making an ESB that calls for

Williamette .5 60 min
Tettnang .5 30 min
Williamette .5 20 min
Tettnang .5 5 min

Unfortunately, because of the low alpha acid in the Williamette, my IBU comes out way low (under 19) with the .5 oz at 60 min, and I don't have any more.

I have Saaz, hallertauer, and Fuggles that I could add. I'm thinking the Fuggles would be the best and probably adding a half oz of it at 60 is a better option than making a not-bitter ESB.

What do you think?

Fuggles is very appropriate for an ESB.

Fuggles is definitely the best choice of those three.

I'll third the Fuggles idea.

Since Willamette is a domestic cultivar of Fuggles, the choice is plain.

Bob