I'm half-way through the process!
Call the following number in the USA to speak to someone at the IRS
They will as sine you a EIN (over the phone) which will then allow you to fill in the W-8BEN. You can find the form online - just do a search - and then send it to :
Amazon Digital Services
Attn: Vendor Maintenance
PO Box 80683
Hope this helps...
(Author of Good Vibrations: Crossing Europe on a Bike Called Reggie)
Do you mind me asking how long the call to the US was and how much it cost? I phoned the IRS office in london and was told to fill in a W-7 and take it with my passport to London (or send it to the London office)