Problem moving cloud sql instance to EU datacentre

I have exported my US instance to google cloud storage, created a new cloud sql instance (EU datacentre) and imported the instance. This is all fine. However when I try to authorize my existing application (appengine, but not the datastore) I get the unknown error problem (we are looking into it). Is my appengine app running on a US datacentre - hence the difficulty in getting it to talk to my new EU cloud sql? I can't see any way to change (or even check) the location of an app engine instance.

Thanks,

Anthony Nolan