We should be cautious when comparing US to UK healthcare. I know this is a US/UK site, but it would also be easy to compare to say South Africa where, I am told by my SA friend, if you don't pay cash upfront for a treatment they roll you outside for the coroner to pick up.
The point that many make with this added fee is that they are already paying taxes that go to the NHS, the same taxes as anyone in the UK, and that this fee is on top of that. THERE IS NO SUCH THING AS FREE NHS HEALTHCARE. It is funded through taxation, just as are the roads or Trident. Imagine driving down the road and as an immigrant being asked to pull over and throw £2 in a bucket every few miles, when you already pay for the roads through various taxes. Not everyone....just you as an immigrant. You might not march on Westminster over it....but it would rankle.
Again, in comparison to the US's notoriously foul system, £200 may not seem like much.......to someone from Haiti?