While the iron overload is the most threatening condition here, it also can create a wide variety of symptoms. It's possible that your esophagus is absorbing too much iron, even though that isn't *typical* in heredity hemochromatosis. E.g., since excess iron is associated with cancer, a study was done to see if there was an association between hemochromatosis and Barrett's Esophagus, which develops down where the esophagus meets the stomach. There wasn't an association found then, but anyway there was enough concern to have run the study. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2670929/
Or maybe it goes the other way round. Some stomach condition possibly results in excess acid, which means you absorb more iron. PPIs would help.
You said: "I have 1 of the genes for haemochromatosis but not the required 2 to be symptomatic."
Well, not necessarily so, or at least there is controversy over that. Those sorts of genetic influences are often not merely all or nothing. Being heterozygous probably can result in a mild case.
From a major health center, John Hopkins, talking about C282Y:
"Clinical hereditary hemochromatosis (HH) generally develops in people with two copies of this mutation, but subgroups of heterozygous individuals have also been identified."
https://www.hopkinsmedicine.org/gastroenterology_hepatology/_pdfs/liver/hemochromatosis.pdf
However, what you consume also has an influence. Maybe along with the lifting, you've been having lots of iron from red meat, etc. and lots of vitamin C. Not all those people even with two copies of C282Y develop the disease, so that means there are other powerful factors at work. You're probably aware that the treatment consists mostly of minimizing iron absorption, plus donating blood (for which they won't make you wait to donate, since donations are down).
I think there's also a prescription chelator, but you're possibly not serious enough for that.
"Sensation of something 'stuck' in oesophagus/top of stomach"
If it doesn't turn out to be silent reflux, then other possibilities to be aware of include Eosinophilic Esophagitis and Achalasia. A possible clue in differentiating is that your feeling of blockage is down by the stomach, not up in the throat.
The advice to keep a food journal to try and identify triggers is sound.
"I have 1 of the genes for haemochromatosis but not the required 2 to be symptomatic."
Take a look are Type 4, which can come about from only one parent (autosomal dominant):
https://rarediseases.info.nih.gov/diseases/10094/hemochromatosis-type-4
However, the NHS doesn't seem to recognize that.
Is your mutation in the SLC40A1 gene?
Good luck.