It's more than likely that what was found was an "artefact." ie of no significance to you medically.
The AME is, however, duty bound to investigate further, due to the nature of your activities. The tests you suggest sound reasonable, I'm not sure about pricing, but about 3-400 quid for each one sounds about right. (Including interpretation).
You may be able to convince your GP for an NHS opinion, but he may find it hard justifying it-and as you may have gathered, communication at the interface isn't one of the NHS strong points.
The important thing is that is unlikely to kill you, and you should, hopefully be in the air again soon- keep us posted.
