As a company (self employed yes) LTD companies are a different matter, don't think you can be a director or certanly not with out approval. Think you can be a company secretary but thats about it. However i am sure someone on here with better experience will be able to answer.
I don't think there's anything stopping you from running a LTD company when discharged although if you were subject to a BRO/BRU then this may stop you. Maybe one the experts will be able help you out on this one.
you may carry on asa sole trader whilst in bankruptcy and of course after discharge and again if you are subject to a BRU/BRO.
To be a director of a limited company you must first be discharged from bankruptcy and if still under restriction of a BRU/BRO you must wait for that to end too.