Hi, presume we're talking about a right bundle branch block.
I have always had a partial RBBB, caused no probs with any licensing. However one year - it became a full RBBB. Video ultrasound of heart (I had to pay and organise privately) then wear halter for 24 hr ecg, see cardiologist at LGW and do stress ECG. Unrestricted class one issued but for 3 years I had to repeat this with the CAA at LGW. Finally decided that was just the way I am and no more checking.
Interestingly for an arduous Asian medical - no probs at all.
I do add this is because of a change from a partial to a full - now partial apparently, might be that a full RBBB is different.
Anyway hope this is of some use. Medical section at LGW was very helpful and easy to deal with.
Best of luck.