Do they have to take my mental health in to consideration

Undervalued

Cam05 said:

As I said I have spoke to my line manager about my issues, and there boss is also aware, 
Even if HR are not aware would it be mitigated circumstances 

That question has already been answered.

It depends on whether your condition amounts to a disability (in law).

If it does then I wouldn't rely on haven just "spoken" to your line manager, as there is no guarantee that he will "remember" the conversation or remember it the way you do!

oh_really

The managers have been informed, was this verbal or by paper-trail?