No I haven't registered with a GP, but I did see a private doctor last year briefly when I was studying abroad. And luckily my medical insurance from the US still covers me when I am here for care, so didn't need to buy travel insurance, either.
However, BUNAC's insurance is done through the same place where my (mandatory) insurance for the study abroad programme was administered, and it was a good deal if I recall. About $300 for the 6 months?