If you have studied, or if you are delivering the IOSH Leading Safely course would you consider it a suitable level of training for the owner of a small contractor company to allow them to operate as their own competent advisor or would you recommend the IOSH Managikng Safely course

We use the courses mentioned to enable the managers to understand what the competent person is telling them, not to make them competent persons.

As Peter has stated, a review of the business's risk profile is crucial to determine the level of competency required. 

The HSe explicitly state"Competence can be described as the combination of training, skills, experience, and knowledge that a person has and their ability to apply them to perform a task safely"

Training is only one piece of the puzzle and should not be viewed as the only avenue to determine competence 

There are some really really incompetent people out there that hold a wealth of qualifications.... and there are some excellent people out there that hold very little. 

It's really important to just be self-aware and ask the question - am I / are you competent (gut feeling will help!) 

I think this has come up on the forum before. The general  consensus was then that as a minimum a competent person needed a Nat cert level qualification, mainly because that ensured a breadth of understanding of how occupational H&S should be applied in a particular workplace. As people have said you need to know what your limits are   and when you need to call in additional help. I am not sure that managing or leading safely do that.