I dont think your right on this Lynne. Im quite sure as a visitor to this country he will be charged to use the NHS. They are also changing settlement to having to have insurance until ILR (so i remember Mel saying about the changes.)
you are right CP, visitor visa holders are not entitled to free NHS care.
they can register with their hosts GP but pay privately for consultation and are not entitled to NHS prescription it is a private script.
in an emergency they can attend A&E any admission to hospital including intensive care or emergency surgery needs to be paid for and can run into thousands.
if they dont pay their bill to the NHS, they will not be issued with another visa in the future.