I had my class 1 two months ago. I am quite slim and athletic and i also got told that they had to consult a GP to clear my ECG. the condition you have is apparently common in slimmer people as it suggests that your hearts pump is large compared to your body mass.. (which defo makes sense in your case). with any luck you will get a phone call from the caa in the next week clearing you with regards to the heart condition. I had the same problem and it worried me for the best part of a week, but the fact is that everyones hearts are slightly different and the condition you have is probably just a variation of normal. hope all goes well!