Hadn't looked in this forum before and this info may be too late - however-
I too have an inverted T-wave. Had to go back to the CAA on initial issue to do an 'exercise' ECG. In my case, it was assessed that I have always had this anomaly - and always will. NO PROBLEM! (or so they tell me). I think the real problem is when, after normal ECGs, you suddenly get a change. I don't have to do anything different - an ECG every year like everyone over 40 and the CAA have never mentioned it since the 'exercise' ECG.
BTW, if an exercise ECG is the same as a stress ECG then get some practice in walking fast uphill! I was told "oh, nothing to worry about, it's just a walk on the treadmill". What they didn't tell me is that the speed and inclination are increased every minute or so and you continue until you can't go on any more!!
Best of luck
BALOO