Difficulties with Google Voice in UK

Location - UK
Phone - Samsung Galaxy S2
Android Version - 2.3.5

When I try and set up my Google Voice app, it asks me to enter a 4 digit PIN, at which stage I get "Your phone number could not be verified. Please try again" every time I try.

I have been advised to log into my Google Voice account and add the number there. Unfortunately, there is no option in my Google Voice account interface to add any numbers.

What I ideally want to do is make outgoing calls from GV and also have an inbound GV number to receive calls.

I have not loaded the GV account with any money yet.

ANy help is greatly appreciated. Thanks in advance.