Yesterday, I had an Upper GI Endoscopy (Gastroscopy).
Despite what you may read and imagine, this doesn't hurt. It isn't the most comfortable thing in the world, but it was an extremely expedient and efficient way to get a diagnosis.
I spent approximately two hours in a nice and clean NHS treatment center (privately run, but available to NHS patients), with friendly helpful staff (stark contrast to the NHS run hospital next door). At the end, the consultant confirmed that I have a small hiatus hernia and non-elusive reflux disorder.
It's just a shame it took >6 weeks to get to see him! At least I can stop worrying now.
The whole experience does make you think that perhaps the hardest job in the world might be "Sword Swallower", though..