Obs Cop.
Don't worry too much. I had a flat T wave throughout my career. (Retired a couple of months ago after holding a Class 1 for 37 years). Still hold a Class 2 for private flying.
I was never referred to a specialist for that problem and was given my initial medical by the RAF CMU, although was referred for a "Left Axial Deviation" Apparently the heart changes position in the chest cavity over time. Mine just changed slightly quicker than the average. When that was investigated I pointed out to the specialist (as I did to any new AME) that they would find the Flat T wave. It did not concern him at all and I was cleared with the Left Axial Deviation.
I have always been of stout girth. When I questioned the condition with one AME he sid it was pretty standard for large chaps. He then showed me the ECG trace of who he referred to as a skinny concorde pilot and the T wave was like Mont Blanc!!
The only interesting thing though was at one of my last medicals the doc said that had I been French and subject to their rules from the word go in the 60's I would not have got a French Medical.
Best wishes