My partner suffers from depression and severe anxiety. He cannot go to even familiar places without being accompanied by someone due to having panic attacks. Despite this, Atos, in their wisdom, scored him 4 points saying he needs prompting to make a journey. Even his ESA85 medical report says that he needs someone with him on unfamiliar journeys, and we included this with the evidence. Despite an MR they have not changed the decision. What is it about them not making mobility awards on mental health grounds now.
This is almost certainly related to the DWP guidance for the Going Out Descriptor that suggests that the issue someone might have can be dealt with by someone providing prompting, we do not believe that this is always the case, have a look at the PIP Claim guide for this descriptor where the issue is discussed in more detail.
I had the same problem, appealed went to tribunal and got Standard mobility because I needed someone with me, this was written on the tribunal notice. Good luck with your tribunal and dont give up.