Right....As a result if all the confusion on here (and because I couldn't remember all the details), I've just rung the number on the web page referenced above.
The very helpful guy on the other end did his best to explain what the current situation is.  I'm going to do a bit more browsing around and see if I can't come up with a definitive post on all this for later.  I'll then ask Nigel if he'll make it a sticky because I think that having the correct information on our health cover is very important to us all.