Can't understand these conditionals :/

[stevepearce]

As much as I try I can't understand why these conditionals are incorrect...

You would have enjoyed yourself if you were there.
(Unreal condition in the present with an unreal past result)

If I weren't driving slowly, he could have been hurt
(Unreal condition in the present with an unreal past result)

I believe these two are mixed conditionals following the same logic as this sentence which I know to be correct....

If I didn't trust him, I wouldn't have let him look after the baby.
(Unreal present condition with unreal past result)

I can't get my head around the differences! :(

[bhaisahab]

As much as I try I can't understand why these conditionals are incorrect...

You would have enjoyed yourself if you were there.
(Unreal condition in the present with an unreal past result)
You would have enjoyed yourself, if you had been there.

If I weren't driving slowly, he could have been hurt
(Unreal condition in the present with an unreal past result)
If I hadn't been driving slowly, he could have been hurt.

I believe these two are mixed conditionals following the same logic as this sentence which I know to be correct....

If I didn't trust him, I wouldn't have let him look after the baby.
(Unreal present condition with unreal past result)
If I hadn't trusted him, I wouldn't have let him look after the baby.

I can't get my head around the differences! :(

Why do you want to use simplified English?

[stevepearce]

I am using Focus on Advanced for C.A.E and it states...

If I didn't trust him, I wouldn't have let him look after the baby.
(Unreal present condition with unreal past result)

Is a correct mixed conditional.

I am aware of the correct answers for the others but I don't know why they are incorrect! The conditionals follow all the rules of conditionals (or I think they do)
but Focus on states that they are incorrect.

Why are they incorrect?