If you're thinking of a post-pay account - where you pay for your calls a month or so after you have made them or pay a monthly amount for an amount of call time - I'm pretty sure they will do a credit check which is likely to involve checking your UK address. Not sure, so I hope somebody else can amplify this.

I'm wondering why you would want to do this for a three month period. The pay-as-you-go market can be very competitive. If you'd like to tell us what kind of calls you'll be making - US, UK, Europe etc - I'm sure we'll have fuller advice.