I've had no problems at all hiring G reg aircraft with my South African licence - though if I want to fly cross border I need to either get a UK CAA licence or fly a ZS reg aircraft!
Now, how would I do this if I wanted to buy a G reg aircraft for export to South Africa - if I wanted to fly it down there on my SA licence? The South Africans require an inspection at an approved facility before it can go on the ZS register - so does that mean I'd need to get a UK validation of my SA licence?
All rather confusing really!