I wonder if you were diagnosed in South Africa, by what means and by whom?
South Africa is medically quite aggressive compared to England and the CAA in Pretoria is infinitely more intransigent than its British counterpart. They're also dumber, less trained, more racist and a thorough going bunch of half witted excuses for doctors-according to a South African specialist I happen to know.
Be that all as it may, if you haven't had the diagnosis confirmed by a UK specialist then perhaps you should do so before you go banging on the CAA's doors telling them that you have it. You want to avoid an OML to start with because, even though they can 'come off' a licence, it's not necessarily the best thing to take into an interview although that caveat would apply more to DICs.
South Africa and the UK do exchange medical information from time to time. You shouldn't volunteer to the South Africans that you have a UK medical or licence. Of course, you mustn't lie either but you want to avoid a telephone exchange between the two authorities.
Bottom line then, if not already done so, get diagnosis confirmed in the UK.
If confirmed then collect every piece of paperwork you can from specialists in order to substantiate your application for a UK medical without an OML or intention for early lifting.
Volunteer nothing to the South African medical department and try to keep them in the dark about your UK licence/medical saga.
I cannot possibly tell you whether your condition will preclude a successful flying career. For further on that I would suggest you follow Radgirl's suggestion, deleting this thread and staring again perhaps.
Best of luck anyway and the above is entirely without prejudice and quite possibly totally bad advice anyway.