Is there a reason the app is not available on the UK app store?
Also, I'd second the recommendation to allow normal signup and put off decisions about trusting the website with contacts. I wanted to sign up while not giving the app access, but was not allowed to go ahead and do that because any emails associated with gmail etc tried to harvest contacts, and the cancel button on the google permissions page doesn't work. Doesn't seem to be a way to register a gmail address without going through the permissions step.
If I want to expose my contacts, I'd rather the app allowed me to choose when and who to do that with, rather than trying to force the choice at signup. I'm happy to give you my email, but not those of all my contacts.
The app is available in the UK store, but Apple's search indices may not have been updated. Try buying it using the direct iTunes link on Quip's website, instead of searching the UK store.
That's strange, I tried it earlier using the link on the website which took me to itunes, and it was listed as not available in my store, but perhaps they fixed the link (might have been a link to the US app) or it was a cache issue as you say. Seems to work now.
Someone else may have mentioned it, but it's really annoying not to be able to do a regular signup through gmail. I don't trust anyone to manage my contacts I'm afraid. Perhaps make those components optional, but just use them for auth?
What types of feedback are you most interested in receiving?