Wrong test, wrong place. What are my rights?

If I'm going to put a stop to my anxiety about LPR reflux, I clearly need a test about what happens in my throat. I looked up a 'double probed pH test' which works like an endoscopy but with a monitor of sorts. I live in Plymouth and they don't do the test - they do single probes which don't check the top of your throat, where all my symptoms occur, importantly! - but Bristol does. I don't care about costs or transport, anything to get results of benefit.

My question is am I within my rights to choose where I get the test done? After suffering for a whole year and counting, the last thing I want is the wrong test, so any help you can offer to help me avoid false-negative results would be much MUCH appreciated!