That doesn't work for me. I have a list of the words my client pays for and I haven't once seen his ads. When I look for generic products like "digital camera" I see a few .au - I bet that people in the UK will see some .uk there but no .au.
My home page is the US Google Advanced Search, yet it makes no difference. It's very much a Layer 3/4 switching kind of trick.
I am not game to risk using an open proxy.