As long as the founding principles of the NHS remain in place, ie, in this case that care received is free at the point of delivery then there is no issue, is there?
What's the difference between a company owning and making a profit from GP services and distributing dividends, and a Senior partner receiving a dividend?
GP practices have always been privately owned, as stated up thread. For instance I needed a dodgy mole seen to a while back, I was sent to a lovely private clinic, seen in minutes, offending article removed a few days later - job done, didn't cost me a penny. All on the NHS - because the clinic could offer the service more cheaply, therefore saving the NHS money.
The whole chemo unit where I used to live is built and run by Virgin. Before they took over people were being given chemo in corridors. All that happens is that the govt pay the company to deliver the service, instead of trying to efficiently manage what was, when I worked in the NHS, a bloody behemoth.
As for the company being American, so what? EDF bought out British Energy, it's now French electrickery - it doesn't mean the kettle boils with a French accent. If the service is the same or better, the ownership makes no difference.
As long as none of the patients at any of those practices gets a bill for their care I don't see the issue.